PS 307 Lecture Notes - Lecture 1: Internal Validity
19 Aug 2017
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Document Summary
Did the independent variable really cause the difference: threats to internal validity: confounding and obscuring variables. Design effect- varies with the independent variable- way it was designed. Selection effect-two independent variable groups has different participants in them. Order effect- in within group design when the effect of the independent variable is cofounded with carryover from one level to the other, or with practice, fatigue or boredom (cid:498)the really bad experiment(cid:499) Maturation effect- naturally your behavior changes over time. History effect- changes over time because of external factor or even that affects most members of the group. Demand characteristics: participants guess what the study"s purpose is and change. Testing- changes overtime because of repeated testing has affected the participants. Instrumentation- an experimental group changes over time because repeated measurements have changed the quality of the measurement instrument. Observer bias: an experimental groups rating differ from a comparison group only because the researcher expects the groups ratings to differ it.
