Chance of getting a first down on 4th & 3 - 70%(or pick any number you want).
Chance of stopping TN on the next series with enough time left to score - 50% (again pick your number).
Chance of scoring a FG or TD on next drive assuming you get the ball back - 40% or 20% (pick your numbers).
There are obviously more variables. But these are the important ones. You'd have to pick some pretty outrageous numbers to make not going for it work, but be my guest and try.
Let's not even start with not going for on 4th & 1. That was another level of stupid.