Psychology 2840F/G Lecture Notes - Lecture 5: Demand Characteristics, Observer-Expectancy Effect

• School: Western University
• Department: Psychology
• Course: Psychology 2840F/G
• Professor: gibson

Document Summary

Design confound another variable varies systematically along with the intended iv. Selection effect kinds of participants in one group are systematically different than the participants in the other group. Order effects participants" later responses are systematically affected by their earlier ones. 6 threats especially relevant to one group designs; maturation, history, attrition, testing, regression, instrumentation: (1) maturation threats. People can naturally mature", i. e. change over time. Preventing maturation threats: appropriate comparison group, to see if people change more in the treatment group the the comparison group: (2) history threats. Something external to an experiment occurs between the pretest and post-test, i. e. historical event, seasonal change. Preventing history threats: use appropriate comparison group: (3) attrition threat. Individuals systematically drop out of the study, must be systematic, i. e. high (or low) scorers on the pretest. Preventing attrition threat: comparison group doesn"t necessarily prevent attrition threat if attrition occurs unequally across conditions: better method: exclude pre test scores of dropouts, (4) testing threats.