Psychology 2800E Lecture Notes - Lecture 17: Sports Illustrated, Observational Error, Repeated Measures Design

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

Document Summary

Background:to say that a causes b a must precede b in time a must covary with b all extraneous variables must be controlled if extraneous variable systematically covaries with iv, then we cannot say that. Iv caused a change in the dv (could be due to external variable) confounding ( threat to internal validity) Types of confounds ( threats to internal validity) A between- group designs ( different groups exposed to different levels of iv) 1 selection: pre-existing differences between groups that define the iv because these differences covary with the iv, they are confounds that prevent us from drawing accurate ( valid) conclusions about cause and effect. Example: effect of seating positions (iv) on grades (dv) does sitting at the front cause students to do better on exams. Groups 2 : sitting at back of room dep var:grades on exams.