Ok Gang,

One more question. Can you elaborate on the following? Specifically what would be the statistic to input into 3dMEMA for testing the -fab interaction? The described algebragic differences are easily enough to compute, but its not intuitive to me what or how generate the corresponding statistic required by the program.

For instance, the F-test for the interaction between factors A and B (both with 2 levels) in this example is essentially equivalent to the t-test (A1B1-A1B2)-(A2B1-A2B2) or (A1B1-A2B1)-(A1B2-A2B2), but we can say more with the t-test than F: a positive t-value shows A1B1-A1B2 > A2B1-A2B2 and A1B1-A2B1 > A1B2-A2B2.

Vinny