Tests supplementing a within-subjects ANOVA are analogous to tests supplementing
to a between-subjects ANOVA. The only differences
lie in the computational details which are taken care of for you by standard
statistical packages. One important computational difference is that when
specific comparisons among means are made on
within-subjects variables, an error term for each specific comparison is
calculated. The same error term is used for all comparisons when the variable
is between-subjects.