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86 Cards in this Set
 Front
 Back
Population

consists of all members of a group


Sample

subset of a population


Descriptive statistics

summarizes the data collected from the sample participants in a study
*summary statistics:measures of central tendency &variability* 

Inferential statistics

allows you to draw conclusions about your data that can be applied to the broader population
bigger samples=more confidence language of 'probability' 

Mean

average


Median

score in the exact middle of a set of scores


Median location

place in the sequence of scores where the median will lie
*(N+1)/2 

Outlier

scores that are far removed from other scores in a data set


Mode

score occuring the most frequently


Range

simplest and crudest measure of variability: difference between high scores and low scores
=highlow+1 

Standard deviation

a measure of the average amount by which the scores in the sample distribution deviate from the mean score (typical distance)
*large is spread out *small is tight around the mean *SS=E(xmean)^2 *=\\/(SS/N) **expresses variability in the same units as original** 

Variance

number calculated just prior to taking the square root of std dev. central feature of "analysis of variance"
*SS/N=popluation *SS/(n1)=sample **corrects for tendency to underestimate for variability 

Histogram

graph that shows thenumber of times each score occurs or how often within a defined range


Frequency distribution

a table that records the number of times that each score occurs


Normal curve

a hypothetical distribution of what all the scores in a population would be like if everyone was tested


Stem and leaf display

often used when there is such a wide range of scores that a simple frequency distribution and histogram would be cumbersome


Null hypothesis

assumption that there is no difference in performance between the different conditions
*can only be rejected,not accepted 

Alternative hypothesis

outcome you are hoping to find


Alpha (a) level

the probability of obtaining your particular results are due to chance
*usually .05 *.01(drug testing) *.10 (pilot study) 

Type I error

Rejecting the null when it is true (Alpha)


Type II error

Fail to reject the null and there is a significant difference (you are wrong) ((Beta)


Systematic variance

the result of some identifiable factor that you have failed to control adequately


Error variance

nonsystematic variability due to individual differences in participants in the two groups


File drawer effect

findings that found no difference and were less likely to be published were stored away in one's files


Effect size

provides an estimate of the magnitude of the difference among sets of scores
*Cohen's D 

Metaanalysis

uses the effect size analyses to combine the results from several experiements that use the same variables with different operational definitions


Confidence Interval

range of values that is expected to include a population value a certain percentage of the time
*tells us that we can be 95% confident that the interval that has been calculated captures the population mean 

Power

the chance of reject the null when it is false (experimenter heaven) ((1Beta))


Experiment

systematic research study in which the investigator directly varies some variable, holds all other factors constant, and observes the resultsof the systematic variation
*investigating the effect of X on Y. 

Independent variable

the factor of interest to the experimenter, the one being studied
*minimum of two levels (2 conditions) 

Field experiment

experiments that take place in the field


Field research

any research outside of the lab, including both experimental and nonexperimental methods


Situational variable

independent variable in which subjects encounter different enviromental circumstances


Task variable

independent variable in which participants are given different types of tasks to perform


Instructional variable

independent variable in which participants are given different sets of instructions about how to perform


Experimental group

group in which the treament is present


Control group

group in which treatment is withheld


Extraneous variable

variables that are not of interest to the researcher but which might influence the behavior being studied if they are not controlled properly


Confound

any uncontrolled extraneous variable that "covaries" with the independent variable and coule provide an alternative explanation of the results


Dependent variable

those behaviors that are the measured outcomes of experiments


Ceiling effect

average scores for the different groups in the study are so high that no difference can be determined: this happens when the dependent measure is so easy that everyone gets a high score


Floor effect

all the scores are extremely low because the task is too difficult for everyone


Subject Variable

a type of independent variable that is selected rather than manipulated by the experimenter; refers to an already existing attribute of the individuals chosen for the study


Statistical conclusion validity

concerns the extent to which the researcher uses statistics properly and draws the appropriate conclusions from the statistical analysis


Construct validity

refers to the adequacy of the operational definitions for both the independent and the dependent variables


External validity

the degree to which research findings generalize beyond the experiment


Subject pool

group of students asked to participate in research, typically as part of an introductory psychology course requirement


Ecological validity

Urlic Neisser: research with relevance for the everyday cognitive activities of people trying to adapt to their environment


Internal validity

the degree to which an experiment is methodologically sound and confoundfree


History

when an event occurs between pre and posttesting that produces large changes unrelated to the treatment program


Maturation

participants change from beginning to end of study


Regression to the mean

first score is high, next score will be closer to the mean


Testing

taking pretest influences posttest scores


Instrumentation

changes in the measurement instrument from pretest to postest


Subject selection

those participating cannot be randomly assigned to groups


Attrition

participants fail to complete a study; people finishing are not equivalent to those who started


Betweensubjects design

any experimentaldesign in which different groups of participants serve in the different conditions of the study


Withinsubjects design

any experimental design in which the same participants serve in each of the different conditions of the study
(repeated measures design) 

Equivalent groups

groups of participants in a betweensubjects design that are essentially equal to each other in all ways except for the different levels of the independent variable


Random assignment

each individual volunteering for the study has an equal probability of being assigned to any one of the groups in the study


Block randomization

a procedure used to accomplish random assignment and ensure an equal number of participants in each condition; ensures that each condition of the study has a subject randomly assigned to it before any condition has a subject assigned to it again
*counterbalancing procedure used in withinsubjects design* 

Matching

a procedure for creating equivalent groups in which participants are measured on some factor expected to correlate with the dependent variable; groups are then formed by taking participants who score at the same level on the matching variable and randomly assigning them to groups


Matching variable

any variable selected for matching participants in a matched groups study


Repeatedmeasures design

another name for withinsubjects design


Sequence (order) effect

can occur in a withinsubjects design when the experience of participating in one of the conditions of the study influences performance in subsequent conditions
*effect internal validity* *sensitization, progressive effect, carryover effect* 

Progressive effect

linear change in performance
practice: improvement across trials fatigue: decline in performance *regardless of particular sequence* (also sensitization) 

Carryover effect

nonlinear, systematic change in performance across experimental conditions resulting from a particular
sequence 

Counterbalancing

for a ws variable, any procedure designed to control for sequence effects
*always for ws design *distribute sequence effects evenly across all conditions 

complete counterbalancing

every possible sequence of experimental conditions is used the same number of times
24 participants=4 conditions (24 sequences) 

incomplete counterbalancing
(Latin Square) 
the most representative sequences of conditions are selected and used the same number of times
ABCD: ABDC BCAD CDBA DACB *only 4 conditions and not enough subjects for comp. cb. 

randomized counterbalancing

different orders are randomly selected from the set of available orders, and one order is randomly assigned to each participant


reverse counterbalancing

participants are tested more than once per condition; subjects experience one sequence, and the a second with the order reversed from the first


Asymmetric transfer

occurs when one sequence produces a transfer effect that is different from that produced by another counterbalanced sequence


Crosssectional study

a design in which age is the independent variable and different groups of people are tested; each group is of a different age


Longitudinal study

a design in which age is the independent variable and the same group of people are tested repeatedly at different ages


Cohort effect

a group of people born at about the same time; cohort effects can reduce the internal validity of crosssectional and longitudinal studies because differences between gruops could result from the effects of growing up in different historical eras


Cohort sequential design

a design that combines crosssectional and longitudinal designs; a new cohort is added to the study every few years


Experimenter bias

occurs when an experimenter's expectations about a study affect its outcome


Protocol

a detailed description of the sequences of events in a research session; used by an experimenter to insure uniformity of treatment of research participants


DoubleBlind

a control procedure designed to reduce bias; neither the participant nor the person conducting the experimental seeiions knows which condition of the study is being tested; often used in studies evaluating drug effects


Participant Bias

can occur when the behavior of participants is influenced by their beliefs about how they are supposed to behave in a study


Hawthorne Effect

name often given to a form of participant bias in which behavior is influened by the mere knowledge that the participant is in an experiment and is therefore of some importance to the experimenter


Good subject Effect
Sensitization 
a form of participant bias in which participants try to guess the experimenter's hypothesis and then behave in such a way as to confirm it
performance later in study differs because hypothesis has been guessed 

Demand Characteristics

any feature of the experimental design or procedure that increases the chances that participants will detect the true purpose of the study


Evaluation Apprehension

a form of anxiety experienced by participants that leads them to behave so as to be evaluated positively by the experimenter


Manipulation Check

in debriefing, a procedure to determine if subjects were aware of a deception experiment's true purpose; also refers to any procedure that determines if systematic manipulations have inteded effect on participants
