Acat Study 3: Experimental Psych

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AB design

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A design in which a baseline condition (A) is measured first, followed by measurements during the experimental intervention (B); there is no return to the baseline condition.

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ABA design

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A design in which a baseline condition (A) is measured first, followed by measurements during the experimental condition (B), followed by a return to the baseline condition (A) to verify that the change in behavior is linked to the experimental condition; also called a reversal design.

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ABAB design

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A design in which a baseline condition (A) is measured first, followed by measurements during a treatment condition (B), followed by a return to the baseline condition (A) to verify that the change in behavior is linked to the experimental condition, followed by a return to the treatment condition (B).

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ABABA design

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A design in which a baseline condition (A) is measured first, followed by measurements during a treatment condition (B), followed by a return to the baseline measurement condition (A), followed by a return to the treatment condition and a final baseline measurement condition (A) to verify that the behavior is linked to the experimental condition.

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Abstract

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A brief summary (approximately 120 words or 960 characters

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Analytic statement

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A statement that is always true.

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Animal rights

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The concept that all sensate species who feel pain are of equal value and have rights.

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Animal welfare

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The humane care and treatment of animals.

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Antecedent conditions

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All circumstances that occur or exist before the event or behavior to be explained; also called antecedents.

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Applied research

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Research that is designed to solve real-world problems.

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A priori comparison

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Statistical test between specific groups that was anticipated, or planned, before the experiment was conducted; also called planned comparison.

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Archival study

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A descriptive method in which already existing records are re-examined for a new purpose.

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At minimal risk

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The subject’s odds of being harmed are not increased by the research.

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At risk

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The likelihood of a subject being harmed in some way because of the nature of the research.

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Balanced Latin Square

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A partial counterbalancing technique for constructing a matrix, or square, of sequences in which each treatment condition (1) appears only once in each position in a sequence, and (2) precedes and follows every other condition an equal number of times.

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Balancing

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A technique used to control the impact of extraneous variables by disturbing their effects equally across treatment conditions.

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Baseline

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A measure of behavior as it normally occurs without the experimental manipulation; a control condition used to assess the impact of the experimental condition.

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Basic research

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Research designed to test theories or to explain psychological phenomena.

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Between-groups variability

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The degree to which the scores of different treatment groups differ from one another (that is, how much subjects vary under different levels of the independent variable); a measure of variability produced by treatment effects and error.

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Between-subjects design

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A design in which different subjects take part in each condition of the experiment.

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Block randomization

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A process of randomization that first creates treatment blocks containing one random order of the conditions in the experiment; subjects are then assigned to fill each successive treatment block.

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Carryover effect

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The persistence of the effect of a treatment condition after the condition ends.

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Case study

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The descriptive record of an individual’s experiences, behaviors, or both kept by an outside observer.

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Causal modeling

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Creating and testing models that may suggest cause and effect relationships among behaviors.

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Cause and effect relationship

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The relationship between a particular behavior and a set of antecedents that always precedes it-whereas other antecedents do not-so that the set is inferred to cause the behavior.

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Changing criterion design

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A design used to modify behavior when the behavior cannot be changed all at once; instead, the behavior is modified in increments and the criterion for success (i.e. reinforcement) changes as the behavior is modified.

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Chi-square (x2)

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A nonparametric, inferential statistic that tests whether the frequencies of responses in our sample represent certain frequencies in the population; used with nominal data.

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Cluster sampling

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A form of probability sampling in which a researcher samples entire clusters, or naturally occurring groups, that exist within the population.

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Coefficient of determination (r2)

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In a Correlational study, an estimate of the amount of variability in scores on one variable that can be explained by the other variable.

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Commonsense psychology

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Everyday, nonscientific collection of psychological data used to understand the social world and guide our behavior.

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Complete counterbalance

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A technique for controlling progressive error that uses all possible sequences that can be formed out of the treatment conditions and uses each sequence the same number of times.

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Concurrent validity

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The degree to which scores on the measuring instrument correlate with another known standard for measuring the variable being studied.

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Confidence interval

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A range of values above and below a sample mean that is likely to contain the population mean with the probability level (usually at 95% or 99%) that the mean of the population (the true mean) would actually fall somewhere in that range.

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Confounding

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An error that occurs when the value of an extraneous variable changes systematically along with the independent variable in an experiment; an alternative explanation for the findings that threatens internal validity.

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Constancy of conditions

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A control procedure used to avoid confounding; keeping all aspects of the treatment conditions identical expect for the independent variable that is being manipulated.

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Construct validity

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The degree to which an operational definition accurately represents the construct it is intended to manipulate or measure.

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Content analysis

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A system of quantifying responses to open-ended questions by categorizing them according to objective rules or guidelines.

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Content validity

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The degree to which the content of a measure reflects the content of what is being measured.

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Context effects

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Effects produced by the position of a question; where it falls within the question order can influence how the question is interpreted.

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Context variable

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Extraneous variable stemming from procedures created by the environment, or context, of the research setting.

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Continuous dimension

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The concept that traits, attitudes, and preferences can be viewed as continuous dimensions, and each individual can fall at any point along each dimension ranging from very unsociable to very sociable.

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Contradictory statement

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A statement that is always false.

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Control condition

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A condition in which subjects receive a zero value of the independent variable.

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Control group

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The subjects in a control condition.

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Convenience sampling

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A convenience sample is obtained by using any groups who happen to be convenient; considered a weak form of sampling because the researcher exercises no control over the representativeness of the sample (also called accidental sampling).

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Correlation

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The degree of relationship between two traits, behaviors, or events, represented by r.

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Correlational study

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A study designed to determine the correlation between two traits, behaviors, or events.

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Counterbalancing

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A technique for controlling order effects by distributing progressive error across the different treatment conditions of the experiment; may also control carryover effects.

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Cover story

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A plausible but false explanation of the procedures in an experiment told to disguise the actual research hypothesis so that subjects will not guess what it is.

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Critical region

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Portion in the tail(s) of the distribution of a test statistic extreme enough to satisfy the researcher’s criterion for rejecting the null hypothesis—for instance, the most extreme 5% of a distribution where p < .05 is the chosen significance level.

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Critical value

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The value of the test statistic that must be exceeded to reject the null hypothesis at the chosen significance level.

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Cross-legged panel design

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A method in which the same set of behaviors or characteristics are measured at two separate points in time (often years apart); six different correlations are computed, and the pattern of correlations is used to infer the causal direction.

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Cross-sectional study

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A method in which different groups of subjects who are at different stages are measured at a single point in time; a method that looks for time-related changes.

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Data

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Facts and figures gathered from observations in research. (Data is the plural form of the Latin work datum.)

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Debriefing

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The principle of full disclosure at the end of an experiment; that is, explaining to the subject the nature and purpose of the study.

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Deductive model

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The principle of reasoning from general principles to specific instances; most useful for testing the principles of a theory.

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Degrees of freedom (df)

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The number of members of a set of data that can vary or change value without changing the value of a known statistic for those data.

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Demand characteristics

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The aspects of the experimental situation itself that demand of elicit particular behaviors; can lead to distorted data by compelling subjects to produce responses that conform to what subjects believe is expected of them in the experiment.

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Dependent variable (DV)

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The specific behavior that a researcher tries to explain in an experiment; the variable that is measured.

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Descriptive statistics

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The standard procedures used to summarize and describe data quickly and clearly; summary statistics reported for an experiment, including mean, range, and standard deviation.

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Deviant case analysis

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A form of case study in which deviant individuals are compared with those who are not to isolate the significant variations between them.

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Directional hypothesis

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A statement that predicts the exact pattern of results that will be observed, such as which treatment group will perform best.

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Discrete trials design

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A design that relies on presenting the averaging across many, many experimental trials, repeated applications result in a reliable picture of the effects of the independent variable.

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Discussion

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Concluding section of the research report, used to integrate the experimental findings into the existing body of knowledge, showing how the current research advances knowledge increases generalizability of known effects, or contradicts past findings.

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Double-blind experiment

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An experiment in which neither the subjects nor the experimenter know which treatment the subjects are in; used to control experimenter bias.

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Effect size

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A statistical estimate of the size or magnitude of the treatment effect(s).

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Elimination

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A technique to control extraneous variables by removing them from an experiment.

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Empirical phenomenology

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Contemporary phenomenology that relies on the researcher’s own experiences, experiential data provided by study participants, or other available sources such as literature or popular media; a qualitative approach.

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Error

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The variability within and between treatment groups that is not produced by changes in the independent variables; variability produced by individual differences, experimental error, and other extraneous variables.

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Experimental condition

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A treatment condition in which the researcher applies a particular value of an independent variable to subjects and then measures the dependent variable; in an experimental group—control group design, the group that receives some value of the independent variable.

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Experimental design

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The general structure of an experiment (but not its specific content).

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Experimental error

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Variation in subjects’ scores produced by uncontrolled extraneous variables in the experimental procedure, experimenter bias, or other influences on subjects not related to effects of the independent variable.

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Experimental group

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The subjects in an experimental condition.

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Experimental hypothesis

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A statement that is a tentative explanation of an event or behavior; it predicts the effects of specified antecedent conditions on a measured behavior.

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Experimental operational definition

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The explanation of the meaning of independent variables; defines exactly what was done to create the various treatment conditions of the experiment.

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Experimentation

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The process undertaken to demonstrate that particular behavioral events will occur reliably in certain specifiable conditions; a principal tool of the scientific method.

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Experimenter bias

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Any behavior of the experimenter that can create confounding in an experiment.

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Ex post facto study

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A study in which a researcher systematically examines the effects of preexisting subject characteristics (often called subject variables) by forming treatment groups based on these naturally occurring differences between subjects.

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External validity

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How well the findings of an experiment generalize or apply to people and settings that were not tested directly.

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Extraneous variable

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A variable other than an independent or dependent variable; a variable that is not the focus of an experiment and that can confound the results if not controlled.

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F ratio

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A test statistic used in the analysis of variance; the ratio between the variability observed between treatment groups and the variability observed within treatment groups.

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Face validity

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The degree to which a manipulation or measurement technique is self-evident.

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Factor

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An independent variable in a factorial design.

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Factorial design

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An experimental design in which more than one independent variable is manipulated.

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Falsifiable statement

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A statement that is worded so that it is falsifiable, or disprovable, by experimental results.

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Falsification

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To challenge an existing explanation or theory by testing a hypothesis that follows logically from it and demonstrating that this hypothesis is false.

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Fatigue effects

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Changes in performance caused by fatigue, boredom, or irritation.

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Field experiment

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An experiment conducted outside the laboratory that is used to increase external validity, verify earlier laboratory findings, and investigate problems that cannot be studied successfully in the laboratory.

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Field study

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A non experimental research method used in the field or in a real-life setting, typically employing a variety of techniques including naturalistic observation and unobtrusive measures or survey tools, such as questionnaires and interviews.

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Focus group

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A type of group interview; it is an organized discussion session with a small group of people, usually led by a trained facilitator.

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Fraud

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The unethical practice of falsifying or fabrication data; plagiarism is also a form of fraud.

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Fruitful statement

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A statement that leads to new studies.

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Good thinking

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Organized and rational thought, characterized by open-mindedness, objectivity, and parsimony; a principle tool in the scientific method.

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Grand mean

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An average of all the treatment group means.

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Higher-order interaction

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An interaction effect involving more than two independent variables.

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History threat

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A threat to internal validity in which an outside event or occurrence might have produced effects on the dependent variable.

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Hypothesis

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The thesis, or main idea, of an experiment or study consisting of a statement that predicts the relationship between at least two variables.

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Hypothetical construct

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Concepts used to explain unseen processes, such as hunger or learning; postulated to explain observable behavior.

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Independent variable (IV)

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The variable (antecedent condition) that the experimenter intentionally manipulates.

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Inductive model

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The process of reasoning from specific cases to more general principles to form a hypothesis.

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Inferential statistics

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Statistics that can be used as indicators of what is going on in a population; also called test statistics.

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Informed consent

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A subject’s voluntary agreement to participate in a research project after the nature and purpose of the study have been explained.

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Institutional animal care and use committee (ASCUC)

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An institutional committee that reviews proposed research to safeguard the welfare of animal subjects.

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Institutional review board (IRB)

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An institutional committee that reviews proposed research to safeguard the safety and rights of human participants.

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Instrumental threat

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A threat to internal validity by changes in the measuring instrument itself.

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Interaction

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The effect of one independent variable changes across the levels of another independent variable; can only be detected by factorial designs.

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Interitem reliability

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The degree to which different items measuring the same variable attain consistent results.

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Internal validity

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The certainty that the changes in behavior observed across treatment conditions in the experiment were actually caused by the independent variable.

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Interrater reliability

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The degree of agreement among different observers or raters.

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Interval scale

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The measurement magnitude, or quantitative size, having equal intervals between values but no true zero point.

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Introduction

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Beginning section of a research report that guides the reader toward your research hypothesis; includes a selective review of relevant, recent research.

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Intuition

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the development of ideas from hunches; knowing directly without reasoning from objective data.

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Large N Data

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A design in which the behavior of groups of subjects is compared.

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Latent content

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The “hidden meaning” behind a question.

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Latin square counterbalancing

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A partial counterbalancing technique in which a matrix, or square, of sequences is constructed so that each treatment appears only once in any order position.

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Laws

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General scientific principles that explain our universe and predict events.

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Level of measurement

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The type of scale of measurement—either ratio, interval, ordinal, or nominal—used to measure a variable.

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Levels of the independent variable

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The two or more values of the independent variable manipulated by the experimenter.

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Linear regression analysis

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A correlation-based method for estimating a score on one measured behavior from a score on the other when two behaviors are strongly related.

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Longitudinal design

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A method in which the same group of subjects is followed and measured at different points in time; a method that looks for changes across time.

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Main effect

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The action of a single independent variable in an experiment; the change in the dependent variable produced by the various levels of a single factor.

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Manifest content

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The plain meaning of the words or questions that actually appear on the page.

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Manipulation check

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An assessment to determine whether the independent variable was manipulated successfully.

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Maturation threat

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A threat to internal validity produced by internal (physical or psychological) changes in subjects.

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Mean

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An arithmetical average computed by dividing the sum of a group of scores by the total number of scores; a measure of central tendency.

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Mean square (MS)

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An average of squared deviation; a variance estimate used in analysis-of-variance procedures and found by dividing the sum of squares by the degrees of freedom.

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Mean square between groups (MSb)

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The variance (or average squared deviation) across different treatment groups produced by error and treatment effects; also the variance about the grand mean.

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Mean square within groups (MSw)

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The variance (or average standard deviation) within a single treatment group; produced by the combination of sources called error.

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Measured operational definition

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The description of exactly how a variable in an experiment is measured.

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Measurement

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The systematic estimation of the quantity of an observable event; a principle tool of the scientific method.

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Measures of central tendency

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Summary statistics that describe what is typical of a distribution of scores; includes mean, median, and mode.

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Median

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The score that divides a distribution in half, so that half the scores in the distribution fall above the median, half below; a measure of central tendency.

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Meta-analysis

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A statistical reviewing procedure that uses data from many similar studies to summarize and quantify research findings about individual topics.

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Method

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The section of a research report in which the subjects and experiment are described in enough detail that the experiment may be replicated by others; it is typically divided into subsections, such as Participants, Apparatus or Materials, and Procedures.

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Methodology

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The scientific techniques used to collect and evaluate psychological data.

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Minimal risk

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The subject’s odds of being harmed are not increased by the research.

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Mixed design

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A factorial design that combines within-subjects and between-subjects factors.

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Mode

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The most frequently occurring score in a distribution; a measure of central tendency.

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Multiple baseline design

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A small N design in which a series of baselines and treatments are compared within the same person; once established, however, a treatment is not withdrawn.

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Multiple correlation

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Statistical intercorrelations among three or more behaviors, represented by R.

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Multiple groups design

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A between-subjects design with one independent variable, in which there are more than two treatment conditions.

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Multiple independent groups design

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The most commonly used multiple groups design in which the subjects are assigned to the different treatment conditions at random.

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Multiple regression analysis

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A correlation-based technique (from multiple correlation) that uses a regression equation to predict the score on one behavior from scores on the other related behaviors.

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Multivariate analysis of variance (MANOVA)

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The statistical procedure used to study the impact of independent variables on two or more dependent variables; an extension of analysis of variance.

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Multivariate design

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Research design or statistical procedure used to evaluate the effects of many dependent variables in combination, including multiple correlation, factor analysis, and multivariate analysis of variance.

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Naturalistic design

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A descriptive, nonexperimental method of observing behaviors as they occur spontaneously in natural settings.

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Nay-sayers

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People who are apt to disagree with a question regardless of its manifest content.

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Negative correlation

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The relationship existing between two variables such that an increase in one is associated with a decrease in the other; also called an inverse relationship.

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Nominal scale

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The simplest level of measurement; classifies items into two or more distinct categories on the basis of some common feature.

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Nondirectional hypothesis

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A statement that predicts a difference between treatment groups without predicting the exact pattern of results.

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Nonequivalent groups design

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A design in which the researcher compares the effects of different treatment conditions on preexisting groups of participants.

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Nonexperimental hypothesis

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A statement of predictions of how events, traits, or behaviors might be related, but not a statement about cause and effect.

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Nonprobability sampling

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Sampling procedures in which subjects are not chosen at random; two common examples are quota and convenience samples.

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Normal curve

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The distribution of data in a symmetrical, bell-shaped curve.

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Null hypothesis (H0)

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A statement that the performance of treatment groups is so similar that the groups must belong to the same population; a way of saying that the experimental manipulation had no important effect.

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Observation

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The systematic noting and recording of events; a principle tool of scientific method.

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One-tailed test

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A statistical procedure used when a directional prediction has been made; the critical region of the distribution of the test statistic (t, for instance) is measured in just one tail of the distribution.

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One-way between-subjects analysis of variance

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Statistical procedure used to evaluate a between-subjects experiment with three or more levels of a single independent variable.

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One-way within-subjects (repeated measures) ANOVA

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Statistic al procedure used to evaluate a within-subjects experiment with three or more levels of a single independent variable.

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Operational definition

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The specification of the precise meaning of a variable within an experiment; defies a variable in terms of observable operations, procedures, and measurements.

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Order effects

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Change in subjects’ performance that occurs when a condition falls in different positions in a series of treatments.

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Ordinal scale

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A measure of magnitude in which each value is measured in the form of ranks.

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Page header

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A header made up of the first few words of your title; used to identify manuscript paes during the editorial process in case the pages get separated.

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Paradigm

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The set of attitudes, values, beliefs, methods, and procedures that are generally accepted within a particular discipline at a certain point in time.

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Parsimonious statement

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A statement that is simple and does not require many supporting assumptions.

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Parsimony

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An aspect of good thinking, stating that the simplest explanation is preferred until ruled out by conflicting evidence; also known as Occam’s razor.

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Partial correlation

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An analysis that allows the statistical influence of one measured variable to be held constant while computing the correlation between the other two measured variables.

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Partial counterbalancing

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A technique for controlling progressive error by using some subset of the available sequences of treatment conditions.

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Participant-observer study

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A special kind of field observation in which the researcher actually becomes part of the group being studied.

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Path analysis

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An important correlation-based method in which subjects are measured on several related behaviors; the researcher creates (and tests) models of possible causal sequences using sophisticated correlational techniques.

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Personality variables

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The personal characteristics that an experimenter or volunteer subject brings to the experimental setting.

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Phenomenology

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A nonexperimental method of gathering data by attending to and describing one’s own immediate experience.

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Physical variables

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Aspects of the testing conditions that need to be controlled.

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Pilot study

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A mini-experiment using only a few subjects to pretest selected levels of an independent variable before conducting the actual experiment.

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Placebo effect

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The result of giving subjects a pill, injection, or other treatment that actually contains none of the independent variable; the treatment elicits a change in subjects’ behavior simply because subjects expect an effect to occur.

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Placebo group

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In drug testing, a control condition in which subjects are treated exactly the same as subjects who are in the experimental group, except for the presence of the actual drug; the prototype of a good control group.

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Plagiarism

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The representation of someone else’s ideas, words, or written work as one’s own; a serious breach of ethics that can result in legal action.

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Population

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All people, animals, or objects that have at least one characteristic in common.

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Position preference

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When in doubt about answers to multiple-choice questions, some people always select a response in a certain position, such as answer b.

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Positive correlation

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The relationship between two measures such that an increase in the value of one associated with an increase in the value of the other; also called a direct relationship.

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Post hoc test

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Statistical test performed after the overall analysis indicates a significant difference; used to pinpoint which differences are significant.

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Power

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The chance of detecting a genuine effect of the independent variable.

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Practice effect

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Change in subjects’ performance resulting from practice.

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Precision matching

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Creating pairs whose subjects have identical scores on the matching variable.

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Predictive validity

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The degree to which a measuring instrument yields information allowing prediction of actual behavior or performance.

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Pretest/posttest design

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A research design used to assess whether the occurrence of an event alters behavior; scores from measurements made before and after the event (called the pretest and posttest) are compared.

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Probability sampling

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Selecting samples in such a way that the odds of any subject being selected for the study are known or can be calculated.

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Progressive error

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Changes in subjects’ responses that are caused by testing in multiple treatment conditions; includes order effects, such as the effects of practice or fatigue.

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Psychological journal

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A periodical that publishes individual research reports and integrative research reviews, which are up-to-date summaries of what is known about a specific topic.

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Psychology experiment

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A controlled procedure in which at least two different treatment conditions are applied to subjects whose behaviors are then measured and compared to test a hypothesis about the effects of the treatments on behavior.

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Purposive sampling

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The selection of nonrandom samples that reflect a specific purpose of the study.

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Qualitative research

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Research that relies on words rather than numbers for the data being collected; it focuses on self-reports, personal narratives, and expression of ideas, memories, feelings and thoughts.

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Quasi-experimental designs

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Often seem like (as the prefix quasi- implies) real experiment, but they lack one or more of its essential elements, such as manipulation of antecedents and random assignment to treatment conditions.

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Quota sampling

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Selecting samples through predetermined quotas that are intended to reflect the makeup of the population; they can reflect the proportions of important population subgroups, but the particular individuals are not selected at random.

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Random assignment

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The technique of assigning subjects to treatment so that each subject has an equal chance of being assigned to each treatment condition.

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Randomized counterbalancing

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The simplest partial counterbalancing procedure in which the experimenter randomly selects as many sequences of treatment conditions as there are subjects for the experiment.

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Random number table

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A table of numbers generated by a computer so that every number has an equal chance of being selected for each position in the table.

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Random selection

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An unbiased method for selecting subjects in such a way that each member of the population has an equal opportunity to be selected, and the outcome cannot be predicted ahead of time by any known law.

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Range

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The difference between the largest and smallest scores in a set of data; a rough indication of the amount of variability in the data.

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Range matching

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Creating pairs of subjects in order of their scores on the matching variable fall within a previously specified range of scores.

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Rank-ordered matching

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Creating matched pairs by placing subjects in order of their scores on the matching variable; subjects with adjacent scores become pairs.

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Ratio scale

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A measure of magnitude having equal intervals between values and having an absolute zero point.

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Raw data

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Data recorded as an experiment is run; the responses of individual subjects

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Reactivity

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The tendency of subjects to alter their behavior or responses when they are aware of the presence of an observer.

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References

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A list of books and articles cited in the research report; placed at the end of a report.

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Regression line

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The line of best fit; represents the equation that best describes the mathematical relationship between two variables measured in a correlational study.

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Reliability

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The consistency and dependability of experimental procedures and measurements; also, the extent to which a survey is consistent and repeatable.

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Repeated-measures design

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A design in which subjects are measured more than once on the dependent variable; same as a within-subjects design.

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Replication

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The process of repeating research procedures to verify that the outcome will be the same as before; a principle tool of the scientific method.

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Representativeness

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The extent to which the sample responses we observe and measure reflect those we would obtain if we could sample the entire population.

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Research report

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Written report of psychological research, which contains four major sections: Introduction, Method, Results, and Discussion.

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Response set

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A tendency to answer questions based on their latent content with the goal of creating a certain impression of ourselves.

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Response style

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Tendency for subjects to respond to questionnaire items in a specific way, regardless of the content.

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Results

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The section of a research report in which the findings are described and the results of statistical tests and summary data are presented.

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Retrospective data

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Data collected in the present based on recollections of past events; apt to be inaccurate because of faulty memory, bias, mood, and situation.

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Reverse counterbalancing

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A technique for controlling progressive error for each individual subject by presenting all treatment conditions twice, first in one order, then in reverse order.

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Risk/benefit analysis

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A determination, made by an institutional review board, that any risk to the individual are outweighed by potential benefits or the importance of the knowledge to be gained.

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Robust

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A term describing a statistical test that can be used without increasing the probability of Type 1 or Type 2 errors even though its assumptions (e.g., the population is normally distributed and has equal variances) are violated.

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Rosenthal effect

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The phenomenon of experimenters treating subjects differently depending on what they expect from the subjects; also called the Pygmalion effect.

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Running head

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A short version of the title, which will appear at the top of pages of the published report.

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Sample of subjects

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A selected subset of the population of interest.

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Sampling

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Deciding who or what the subjects will be and selecting them.

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Scatterplot

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A graph of data from a correlational study, created by plotting pairs of scores from each subject; the value of one variable is plotted on the X (horizontal) and Y (vertical) axis.

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Science

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The systematic gathering of data to provide descriptions of events taking place under specific conditions, enabling researchers to explain, predict, and control events.

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Scientific method

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Steps scientists take to gather and verify information, answer questions, explain relationships, and communicate findings.

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Scientific writing style

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A concise, impersonal, and unbiased form of writing used in research reports.

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Selection interactions

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A family of threats to internal validity produced when a selection threat combines with one or more of the other threats to internal validity; when a selection threat is already present, other threats can affect some experimental groups but not others.

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Selection threat

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A threat to internal validity that can occur when nonrandom procedures are used to assign subjects to conditions or when random assignment fails to balance out differences among subjects across the different conditions of the experiment.

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Serendipity

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The knack of finding things that are not being sought.

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Shorthand notation

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A system that uses numbers to describe the design of a factorial experiment.

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Significant level

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The statistical criterion for deciding whether to reject the null hypothesis or not.

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Simple correlations

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Relationships between pairs of scores from each subject.

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Simple random sampling

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The most basic form of probability sampling whereby a portion of the whole population is selected in an unbiased way.

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Single-blind experiment

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An experiment in which subjects are not told which of the treatment conditions they are in; a procedure used to control demand characteristics.

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Small N Design

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A design in which just one or a few subjects are used; typically, the experimenter collects baseline data during the initial control condition, applies the experimental treatment, then reinstates the original control condition to verify that changes observed in behavior were caused by the experimental intervention.

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Snowball sampling

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A form of nonprobability sampling in which a researcher locates one or a few people who fit the sample criterion and asks these people to locate or lead the research to additional individuals who fit the criterion.

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Social variables

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The qualities of the relationships between subjects and experimenters that can influence the results of an experiment.

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Standard deviation

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The square root of the variance; measures the average deviation of scores about the mean, thus reflecting the amount of variability in the data.

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Statistical conclusion validity

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The degree to which conclusions about a treatment effect can be drawn from the statistical results obtained.

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Statistical inference

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A statement made about a population and all its samples based on the samples observed.

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Statistical regression threat

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A threat to internal validity that can occur when subjects are assigned to conditions on the basis of extreme scores on a test; upon retest, the scores of extreme scorers tend to regress toward the mean even without any treatment.

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Statistical significance

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Meeting the set criterion for significance; the data do not support the null hypothesis, confirming a difference between the groups that occurred as a result of the experiment.

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Statistics

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Quantitative measurements of samples; quantitative data.

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Stratified random sampling

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A form of probability sample obtained by randomly sampling from people in each important population subgroup in the same proportions as they exist in the population.

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Subject

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The scientific term for an individual who participates in research.

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Subject-by-subject counterbalancing

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A technique for controlling progressive error for each individual subject by presenting all treatment conditions more than once.

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Subject mortality threat

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A threat to internal validity produced by differences in dropout rates across the conditions of the experiment.

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Subject variable

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The characteristics of the subjects in an experiment or quasi-experiment that cannot be manipulated by the researcher; sometimes used to select subjects into groups.

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Sum of squares (SS)

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The sum of the squad deviations from the group mean; an index of variability used in the analysis-of-variance procedures.

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Sum of squares between groups (SSb)

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The sum of the squared deviation of the group means from the grand mean.

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Sum of squares within groups (SSw)

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The sum of the squared deviations of subjects’ scores from the group mean.

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Summary data

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Descriptive statistics computed from the raw data of an experiment, including the measures of central tendency and variability.

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Survey research

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A useful way of obtaining data about people’s opinions, attitudes, preferences, and experiences that are hard to observe directly; data may be obtained using questionnaires or interviews.

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Synthetic statement

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A statement that can either be true or false, a condition necessary to form an experimental hypothesis.

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Systematic observation

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A system for recording observations; each observation is recorded using specific rules or guidelines, so observations are more objective.

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Systematic random sampling

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A variation of random sampling in which a researcher selects every nth person from the population.

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t test

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A statistic that relates differences between treatment means to the amount of variability expected between any two samples of data from the same population; used to analyze the result of a two group experiment with one independent variable and interval or ratio data.

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t test for independent groups

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A statistic that relates differences between treatment means to the amount of variability expected between any two samples of data from the same population; used to analyze the results of a two group experiment with independent groups of subjects.

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t test for matched groups

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A statistic that relates differences between treatment means to the amount of variability expected between any two samples of data from the same population; used to analyze two group experiments using matched-subjects or within-subjects designs. Also called a within-subjects t test.

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Testable

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Capable of being tested; typically used in reference to a hypothesis. Two requirements must be met to have a testable hypothesis: procedures for manipulating the setting must exist, and the predicted outcome must be observable.

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Testable statement

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A statement that can be tested because the means exist for manipulating antecedent conditions and for measuring the resulting behavior.

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Testing threat

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A threat to internal validity produced by a previous administration of the same test or other measure.

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Test-retest reliability

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Consistency between an individual’s scores on the same test taken at two or more different times.

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Test statistics

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Statistics that can be used as indicators of what is going on in a population and can be used to evaluate results; also called inferential statistics

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Theory

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A set of general principles that attempts to explain and predict behavior or other phenomena.

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Title

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The name of the report, which describes what the report is about; typically includes the variables tested and the relationship between them.

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Treatment

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A specific set of antecedent conditions created by the experimenter and presented to subjects to test its effect on behavior.

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Two experimental groups design

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A design in which two groups of subjects are exposed to different levels of the independent variable.

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Two factor experiment

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The simplest factorial design, having two independent variables.

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Two group design

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The simplest experimental design, used when only two treatment conditions are needed.

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Two independent groups design

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An experimental design in which subjects are placed in each of two treatment conditions through random assignment.

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Two matched groups design

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An experimental design with two treatment conditions and with subjects who are matched on a subject variable thought to be highly related to the dependent variable.

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Two-tailed test

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A statistical procedure used when a nondirectional prediction has been made; the critical region of the distribution of the test statistic (t, for instance) is divided over both tails of the distribution.

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Type 1 error

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An error made by rejecting the null hypothesis even though it is really true; stating that an effect exists when it really does not.

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Type 2 error

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An error made by retaining the null hypothesis even though it is really false; failing to detect a treatment effect.

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Unobtrusive measure

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A procedure used to assess subjects’ behaviors without their knowledge; used to obtain more nonreactive data.

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Validity

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The soundness of an operational definition; in experiments, the principle of actually studying the variables intended to be manipulated or measured; also, the extent to which a survey actually measures the intended topic.

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Variability

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Fluctuation in data; can be defined numerically as the range, variance, or standard deviation.

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Variance

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The average squared deviation of scores from their mean; a more precise measure of variability than the range.

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Willingness to answer

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The differences among people in their style of responding to questions they are unsure about; some people will leave these questions blank, whereas others will take a guess.

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Within-groups variability

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The degree to which the scores of subjects in the same treatment group differ from one another (that is, how much subjects vary from others in the group); an index of the degree of fluctuation among scores that is attributable to error.

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Within-subjects design

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A design in which each subject takes part in more than one condition of the experiment.

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Within-subjects factorial design

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A factorial design in which subjects receive all conditions in the experiment.

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Yea-sayers

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People who are apt to agree with a question regardless of its manifest content.