PSYB04H3 Lecture Notes - Lecture 9: Blind Experiment, Observer-Expectancy Effect, Internal Validity
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Psyb04h3 week 8 experimental methods part ii. Degree to which we can conclude that the changes in iv caused the changes in dv. How should researcher control each of these factors. Selection effect: differences between the groups: random assignment. Maturation: natural changes in participants over time: comparison group. History: historical event affects outcome: comparison group. Regression to the mean: unusually high or low scores followed by measurements that are closer to group mean: comparison group and close examinations. Testing: participants change due to testing: eliminate pretest, use alternate forms. Instrument change: not using the same measurement tools or methods with each subject: recalibration, interrater calibrations. Mortality (attrition) subjects dropping out: carefully examine data, remove scores if appropriate. Experimenter bias (observer bias: blind or double blind procedure. Demand characteristics: blind or double-blind procedure. Participant bias: participant expectations can affect their behavior. If expectations of one group is different from expectations from another group.
