what is repeated measures design
same subjects are in each condition
assumptions of repeated measures ANOVA
1) normal distribution
2) homogeneity of variance
3) sphericity
what is the sphericity assumption
standard errors of the differences between pairs of cell means in repeated measures design are constant
what does it mean if compound symmetry exists
both homogeneity of variance and sphericity assumptions are met
however, sphericity assumption can be met without compound symmetry
what statistical test is used for the sphericity assumption
if test is significant, what do you do
mauchly sphericity test
you adjust the degrees of freedom by a correction factor called epsilon
in within subjects designs, participants are doing stuff multiple times, so you can look at the variance between them
what does SStotal, SSbetween, SSwithin, SSmodel, and SSerror mean
SStotal: total variance in data
SSBetween: variance between subjects
SSwithin: variance within subjects
SSmodel: variance explained by model
SSerror: unexplained variance
strengths and weaknesses of between subjects designs
Individual differences increase MS(Error)
Less prone to carryover effects and demand characteristics
strengths and weaknesses of within subjects designs
Prone to carryover effects and demand characteristics
Controls variability due to individual differences or other “matching” variables with corresponding reduction in MS(Error)
