Can a test statictic value be negative?

Question

I used SAS and performed a t-test. The t-value for unequal variances is -3.21. I've never seen a negative t-value before in class. Is this possible or did I enter an error in SAS?

Answer 1

If I shake the cobwebs out of my head, I think the statistic of the t test can be negative. The usual set-up is that you have 2 sets of data with 2 means t1 and t2, and your test is for t2-t1/(some measure of standard deviation). The actual theorm is based on t^2 / variance, which is always positive.