Why going for it was right
facing 4th and 2, the Pats had about a
60% of getting the first down. This of course would have ended the game. 60% is a historical league average, you can quibble with this figure up or down if you want, but thats around the ballpark % chance the Pats make it.
so if they will convert 60% of the time, then going for it gives them a
Win Probability of at least 60%. I say "at least" b/c even if the fail to convert, the Pats still have a chance of stopping the Colts from the 30. what % is that? the league average in this situation is around 53%, though I think we would agree that the Colts vs our defensive had a much higher % chance of scoring. call it...75% ? that means 25% of the time, even when we don't get the first down, we win by stopping the Colts.
so,
(0.60 * 1) + (0.40 * (1-0.75)) = 70% Win Percentage for Pats
the alternative move of course is to Punt, which on average will put the Colts right around their 34. (again, these #'s are taken from the above link).
what are the odds the Colts drive down and score now? We used 75% chance from the Pats 30, so it's obviously going to be much less from their own 34. The historical league average is 30% in this situation, but again I think it's higher than that. Call it 45%. that means the Pats have a 55% Win Probability from punting.
given those assumptions above, going for it leads to pats victories 70% of the time while punting leads to victories 55% of the time. you can play around with those #'s yourself and change the assumptions, but you would need to plug in some weird #'s to come to a conclusion that says punting is the right move.
2nd point:
in terms of the decision making process, the results don't matter. the decision to punt or not punt is not made correct or incorrect by what happens afterwards. to call decisions "right" or "wrong" based solely on the results is horribly incorrect "analysis". sometimes Faulk gets to the 30, sometimes he doesn't, but either way going for it was right. sometimes the result is going to look bad, sometimes it won't. you need to divorce yourself from the results if you want to learn how to make the best decision.