groups one with and one without the pretest and in the two experimental groups

Groups one with and one without the pretest and in

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groups (one with and one without the pretest) and in the two experimental groups (one with and without the pretest) Posttest-only design: when no pretest is given in an independent groups design * read over study stuff on pg 163 (?) Repeated measures design Repeated measures design: participants are repeatedly measured on the dependent variable after being in each condition of the experiment; also called within-subjects design - Fewer participants are needed - Extremely sensitive to finding statistically significant differences between groups – data are from the same people so there is less error variance o Individual variability is part of random error in the scores that we cannot explain o We are much more able to detect an effect of the independent variable on the dependent variable, if one exists o One disadvantage could be an order effect: the order of presenting the treatments affects the dependent variable Practice effect: an improvement in performance as a result of repeated practice with a task Fatigue effect: a deterioration in performance as the research participant becomes tired, bored, or distracted Time-related order effects are possible whenever there is a sequence of tasks to perform Contrast effect: occurs when the response to the second condition in the experiment is altered because the two conditions are contrasted to one another Two approaches to dealing with the problem of order effects in repeated measures design: (1) to employ counterbalancing techniques and (2) to devise a procedure in which the interval between conditions is long enough to minimize the influence of the first condition on the second Counterbalancing Complete counterbalancing - All possible orders of presentation are included in the experiment - It is possible to determine the extent to which order is influencing results - The number of orders possible increases quickly as more conditions are added
Partial counterbalancing Latin square: a limited set of orders constructed to ensure that (1) each condition appears at each ordinal position and (2) each condition precedes and follows each condition one time -

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• Fall '15
• Dr. Ostovich
• researcher

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