> Thanks for sending that link. It seemed helpful for analyzing three conditions relative to a threshold

Jena, I'm not so sure what you mean by 'threshold'; if you're referring to letter D in the example on my website, D is indeed meant to be a condition, not some threshold.

Applying the same method to your situation,

> cond1 > cond2 = cond3
> cond1 = cond2 > cond3
> cond1 > cond2 > cond3

you can define the following scenarios:

cond1 > cond2 ==> 1 with threshold athresh
cond2 > cond3 ==> 2 with threshold bthresh
cond1 not different from cond2 ==> 4 with threshold athresh
cond2 not different from cond3 ==> 8 with threshold bthresh

and then run 3dcalc with the following

-expr 'step(a-athresh) + 2*step(b-bthresh) + 4*step(athresh-abs(a)) + 8*step (bthresh-abs(b))' -a TstatisticFORcond1-cond2 -b TstatisticFORcond2-cond3

In the output,

9 means cond1 > cond2 = cond3;
6 means cond1 = cond2 > cond3;
3 means cond1 > cond2 > cond3; and
you can figure out the other scenarios by the same token.

HTH,
Gang