I don't know.

It all is situational to me. It depends on who is raising, how good they are, their position, how strong my pair is and how many callers there are. Set hands tend to be very profitbale, especially when an Ace flops with your set (say I have 66 and the flop is A,J,6). Also, if the raise is kind of high, like $2.50 or so, but 3 players call, I will take a chance with a hand like 33 or 44 on the chance of a big payout if it hits.