st: Basic regression interaction term question

["Michael I. Lichter" <mlichter@buffalo.edu>]

This is a pretty basic question, but I haven't been able to find any 
examples in the lit with this particular configuration ...

Suppose you regress Y on A and B, and you expect an interaction between 
A and B.

In the regression Y = A + B, the coefficient for B is not significant, 
but you have reason to think that it will be significant once you 
introduce the interaction term.

However, in the regression Y = A + B + AB, the coefficient for B remains 
non-significant even though the coefficient for AB is significant. Yet, 
"test A B AB" is significant.

Is it reasonable to treat this as a significant interaction?

What if AB is not significant either but "test A B AB" is still significant?

Michael
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