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Psyc ch 6: Threats to internal validity
extraneous variables and confounding variables; A HERMIT
failure of random assignment
an outside event influences Ps' scores in one condition more so than another
environments differ from one treatment condition to another
regression (to the mean)
extreme scores at one point in time tend to be less extreme at next measurement
Ps grow or change over course of study
changes in measuring over time affect results
Testing effects (Order effects)