Yesterday the Wall Street Journal’s Numbers Guy blogged about the recent SI article on the high school team coached by Kevin Kelly that never punts.http://blogs.wsj.com/dailyfix/2009/09/18/the-count-its-fourth-and-long-go-for-it/.
The SI article also mentioned that the high school coach always onside kicked because his team recovered 25 % of the onside kicks and he estimated that other team got the ball on their 33 yard line on average when he kicked deep and on their 48 yard line when he kicked onside.
Plugging in our point values for every yardline (described in my new book Mathletics) we find that a high school team should kick onsides if they have at least a 28% chance of recovering the kick. Thus Coach Kelly was not far off.
In the NFL teams kick off from the 30 yard line (in high school the 40 yard line) and we estimate that you need at least a 52% chance to recover an onside kick to make it worthwhile.
Of course, near the end of the game if you are down, you need to onside kick, but in this post we are talking about a team that simply wants to mazimize its expected margin of victory.