PSYC 2030 Study Guide - Final Guide: Internal Validity, Observer-Expectancy Effect, Demand Characteristics

• School: York University
• Department: Psychology
• Course: PSYC 2030
• Professor: Raymond A Mar

Document Summary

The passage of time - big problem in experiments that have within subject designs where participants make a number of responses. Both participants and circumstances change, not the treatment. History effects threat to internal validity posed by events occurring between two experimental observations. These events can be of both major import or relatively mundane. Any changes in the participants" circumstances that take place over the course of a study. Maturation and history effects pose threats to internal validity because they result in the participants not being completely identical at pre-test and post test phases of an experiment. This can lead to systematic differences between observations at different phases of a study. Testing effects: threats to internal validity that arise when responses on one dependent measure affect responses on another. Reactivity: change in dependent variables caused by obtaining responses on those dependent variables. This threat to internal validity is often posed by participants" reactions to particular experimental procedures or measures.