PSYC 251 Lecture Notes - Lecture 6: Blind Experiment, Demand Characteristics, Neuroimaging
Document Summary
Without random assignment and manipulation we have only correlations. If x is related to y, we don"t know if x causes y, y causes x or some other variable causes both. When participants can be randomly assigned to different levels of the iv. When participants cannot be randomly assigned to different levels of all the ivs. When two or more groups of unrelated participants are tested in separate conditions. Each group/condition is determined by a level of an iv. If individual differences are systematically different between groups they can create effects (extraneous variables/confounds) More participants are needed for these designs (expensive, time consuming) When the same participants take part in every condition. Each condition therefore has the same number of participants (since it literally has the same participants) Fewer participants needed (saves time and energy) Because the same participants are in each condition, individual differences across conditions do not vary. Order effects - order, practice, carryover, fatigue.
