PSYCH 303 Lecture Notes - Lecture 7: Internal Validity, Dependent And Independent Variables, Random Assignment
11 Mar 2018
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Outline: experimental designs, between groups designs, within-groups designs. In a true experiment, the only difference is the level of the independent variable, which shows internal validity: established by well-designed experiments. Design confounds: a design confound is when a second variable varies systematically along with the iv and provides an alternative explanation for the results. Experimental design: select conditions/levels of iv, design within or between subjects, equate groups with random assignment, apply manipulation, standardize procedure, counterbalance, remove confounds, measure outcome (dv) Design: within-subjects design is when each subject gets each treatment, and serves as his or her own control. Effect depends on position, anything that comes last will not fare well. Change order of conditions for different participants: practice effects, carryover effects, sequence effects: effect depends on what precedes it. This happens when doing a particular condition has an effect on the next condition.
