Fixed and Random Effects in ANOVA • All of interest - fixed • Sample of interest – random • Difference in expected means and variance components
Fixed and Random in M-A • Has two meanings • As in ANOVA, generalizable vs not • Single value or underlying distribution • Single Population Value • Fixed • Distribution of Population Values • Random • Test Validation Example • Mixed Model • Fixed Moderators • Remaining variance
Random Effects Case 1 A single, unknown moderator.
Random Effects Case 2 Lots of little moderators.
Numerical Illustration Correlations [r] from five studies from fixed- and random-effects scenarios. The mean for both scenarios would be .5 over an infinite number of studies.