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PSY 121
Chapter 8
Term | Definition |
---|---|
independent groups | aka between-subjects design, random assignment of participants to one condition, different participants in each condition |
repeated measures | aka within-subjects design, same participants used in all conditions, less participants needed, greater control over participant differences, greater ability to detect effect of IV |
mixed assignment | both independent groups and repeated measures assignment are used |
confounding | occurs when the effects of an IV and an uncontrolled variable are intermixed or intertwined and you cannot ascertain which of the variables is responsible for the observed effect. They directly affect internal validity |
posttest only design | obtain 2 equivalent groups of participants, randomization, no selection difference, must introduce IV (2 levels), must measure the effect of IV on the DV |
pretest - posttest design (2 groups) | obtain 2 equivalent groups, randomization, pretest measure introduced prior to manipulation, ensures equivalency, comparison, IV (2 levels) measure the effect of IV on the DV (same measure for both groups) |
one group pretest-posttest design | "one shot case study." low internal validity, measure participants before manipulation and then again afterward |
practice effects (order effects) | performance improves as study progresses |
fatigue effects (order effects) | performance deteriorates as study progresses |
carryover effects (order effects) | effect of 1st condition affects performance in 2nd condition, can be used up to three conditions |
complete counterbalancing | all possible order of presentation are included in the experiment |
latin square | A technique that controls for order effects without having all possible orders. Used in 4 or more conditions |
matched pairs design | match groups on a certain characteristic related to the DV. |
steps involved in matched pairs design | Steps Involved: Measure the matching variable for each RP Rank order RPs from highest to lowest based on scores obtained. Form pairs that are equal on the matching variable. Randomly assign one member of each pair to a condition |