Hi, I haven't recieved any replies to my last email, so let me be a bit more specific. I have a dataframe and it has the following structure: Condition Mapping Subject A B C 1 1 5 10 15 1 2 1 3 1 4 1 5 1 6 1 7 1 8 2 9 2 10 Mapping is a between-subject factor. Condition is a within-subject factor. There are 5 levels of mapping, 8 subjects nested in each level of mapping. For each of the 40 combinations of mapping and subject there are 3 observations, one in each level of the condition factor. I want to estimate the pooled error associated with the following set of 4 orthogonal contrasts: condition.L:mapping.L condition.L:mapping.Q condition.L:mapping.C condition.L:mapping^4 What is the best way to do this? One way is to estimate the linear contrast for condition for each subject, create a 40 row matrix where the measure for each combination of mapping and subject is the linear contrast on condition. If I pass this dataframe to aov, the mse it returns is the value I am looking for. If possible, I would like to obtain the estimate without collapsing the dataframe, but am not sure how to proceed. Suggestions? Steve [[alternative HTML version deleted]]