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86 Cards in this Set

  • Front
  • Back
consists of all members of a group
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'
score in the exact middle of a set of scores
Median location
place in the sequence of scores where the median will lie

scores that are far removed from other scores in a data set
score occuring the most frequently
simplest and crudest measure of variability: difference between high scores and low scores

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
**expresses variability in the same units as original**
number calculated just prior to taking the square root of std dev. central feature of "analysis of variance"

**corrects for tendency to underestimate for variability
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
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
the chance of reject the null when it is false (experimenter heaven) ((1-Beta))
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
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 confound-free
when an event occurs between pre- and posttesting that produces large changes unrelated to the treatment program
participants change from beginning to end of study
Regression to the mean
first score is high, next score will be closer to the mean
taking pretest influences posttest scores
changes in the measurement instrument from pretest to postest
Subject selection
those participating cannot be randomly assigned to groups
participants fail to complete a study; people finishing are not equivalent to those who started
Between-subjects design
any experimentaldesign in which different groups of participants serve in the different conditions of the study
Within-subjects 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 between-subjects 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 within-subjects design*
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
Repeated-measures design
another name for within-subjects design
Sequence (order) effect
can occur in a within-subjects 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
non-linear, systematic change in performance across experimental conditions resulting from a particular
for a w-s variable, any procedure designed to control for sequence effects

*always for w-s 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

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

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