Contrasts with Proc GLM

[Chewbecca]

I have a design with two levels of an A independent variable and two levels of a B independent variable. I am interested in testing whether levels A2 B2 are significantly different from A1 B1. I've set up the following contrast statements and am not sure how SAS is reading them, because I'm getting very different numbers for both:

contrast '1' A -1 1 B -1 1;
contrast '2' A*B 1 -1 -1 1;

Just a description of the difference between these (i.e. how SAS is interpreting them) would be greatly appreciated!

[PaigeMiller]

Contrast 1 compares levels of the main effects of A and B

Contrast 2 compares levels of the interaction between A and B