Psychology 2800E Lecture Notes - Lecture 20: Internal Validity, Hawthorne Effect

• School: Western University
• Department: Psychology
• Course: Psychology 2800E
• Professor: Patrick Brown

Document Summary

History: occurrence of an event other than the treatment. Maturation: participants always change as a function of time (is change due to something else?) Testing: improvement due to practice on tests (familiarity w procedure or w expectations) Instrumentation: especially if humans are used to assess behaviour (fatigue, practice) Regression to the mean: when rst observation is extreme, next is likely to be close to mean. Selection: if differences b/t groups exist from the outset of a study. Mortality: if exit from a study is not random, groups may end up very different. 1/+ groups respond differently to effects of history, maturation or instrumentation. Eg. compare; maturation = one group; performance better on post test than pre test. Interaction of maturation & selection; 2/+ groups; performance difference larger on post test than pre test. Sometimes cannot bring the phenomenon we want to study into the lab, so we have to work in the eld. Have to work w intact groups (classes)