Originally Posted by sltr

What do the data say? Here's Science News' summary of a recent analysis of icing by Scott Berry and Craig Wood in Chance.
Berry and Wood analyzed data about field goal attempts during the 2002 and 2003 NFL seasons (including playoffs). They recorded the kicker, the length of the kick, the score of the game, the time left in the game, and whether a timeout was called by the defense before the kick. They even noted whether the field was grass or artificial turf and the weather conditions (sun, clouds, rain, snow, average wind speed, temperature--?unless the games were indoors).

In these two seasons, there were 52 different field goal kickers, combining for a total of 2,003 attempts. Of these kicks, 1,565 (78.1 percent) were successful.

Berry and Wood then looked at what they defined as "pressure" kicks--?those that occurred with 3 minutes or less remaining in the game (or overtime) and would create a lead or a tie for the team attempting the kick.

There were 139 such pressure kicks, and 101 (73 percent) were successful. The defense called a timeout 38 times before the pressure kick, and 24 (63 percent) of these kicks succeeded.
Berry and Wood also estimate a probability model which allows for the influence of factors like weather to be captured. The results appear sensible, and the "icing effect" remains.
A kick made indoors is more likely to be successful. Clouds also have a small beneficial effect on kicks. Rain or snow, on the other hand, reduces the chances of success. High winds also reduce the probability of success, but not as much as rain or snow.

In pressure situations, the odds of success change very little (a mean decrease of 1.8 percent). However, icing the kicker in such a situation has a pretty strong negative effect.

Using their model, Berry and Wood calculate that, for an average kicker, the estimated probability of a successful 40-yard kick in sunny weather is 0.759. The estimated probability under the same conditions for an average kicker who has been iced is 0.659. "Reducing the probability of a successful kick from 0.759 to 0.659 is a very important difference," Berry and Wood report.