PSYC 201W Lecture Notes - Lecture 7: Repeated Measures Design, Desalination, Internal Validity

• School: Simon Fraser University
• Department: Psychology
• Course: PSYC 201W
• Professor: Russell Day

Document Summary

Advantages of repeated measures or within subjects design: Chapter 7: fewer participants needed, unexplained variability in the dv is reduced, each subject acts as their own control; the effect of individual differences is eliminated; experiment is more sensitive. Research design: outline, plan or strategy used to investigate the research problem. Purpose: control unwanted variation, suggests how data will be statistically analyzed. Goal: choose strongest design that is possible, ethical and feasible. Internal validity threats: no assurance of equality of groups b/c they were not randomly assigned, may confound selection (additive & interaction effects). Strong experimental designs: designs that effectively control extraneous variables and provide strong evidence of cause. Improved internal validity achieved by eliminating rival hypotheses: control techniques (random assignment, control group), between-participants design, different groups are exposed to different levels of iv, does not guarantee equivalence of groups, no pre-test to assess equivalence.