Psychology 2800E Lecture Notes - Lecture 15: Control Order, Random Assignment, Internal Validity

• School: Western University
• Department: Psychology
• Course: Psychology 2800E
• Professor: Doug Hazlewood

Document Summary

Different groups get different conditions of iv: e. g. , 2 levels (or conditions): Control group (subjects 11-20: or multiple levels (conditions), e. g. , High treatment group (21-30: within-group or (within-subjects) All participants exposed to all levels of iv: experimental condition (subjects 1-10, control condition (same subjects 1-10) Can also have multiple conditions if iv has more than 2 levels (all p"s will still be in all conditions: mixed-factorial (or mixed ) design. Mixed : 1 iv manipulated within subjects, 1 iv manipulated between groups. See next lecture (and ch 11) for more on factorial experiments. Example 1: pretest-treatment-posttest design (aka: one group pretest-posttest design p. Better than: one group posttest-only design (p. 262, posttest-only with ne control groups (p. 262) But: has many threats to internal validity: must add a no treatment control group a mixed design, pre vs. post is within subjects, treatment vs. no treatment is between groups. Example 2: evaluating golf balls ( a and b )