Saturday, 29 January 2011

 Overtime .....Not Just a 50/50 Coin Toss (Mark 2).

Conventional wisdom appears to suggest that after two teams have played a stalemate after 4 quarters,any pre game advantage enjoyed by the better side has vanished.It's assumed that before the overtime coin toss the game is considered a 50/50 proposition and after the coin toss the team electing to receive the ball now has around a 60% chance of winning and that increased chance of winning is solely as a result of receiving the ball first.

However,in a previous Overtime post I presented figures which showed that the better side from a pregame perspective still wins more often in overtime.In this post I hope to show that there can be little doubt that pre game favouritism does indeed carry over into overtime.Results used were from the 1995 season onwards because the kickoff was moved to the 30 yardline from this season onwards.Pregame favourites were determined by a regression model based on passing and rushing efficiency on both sides of the ball.

The earlier post used results stretching back to1989,so to firstly ensure that only games since the latest kickoff rule change were included I repeated the analysis using post 1994 games.

The sample size comprised just over 250 games and once again the pre game favourite did better in overtime,winning 58% of the overtime contests.(Non playoff games that ended scoreless after one period of overtime were credited as half a win to each team).
However,this opened up the possibility that pregame favourites were merely being lucky at guessing the coin toss and their winning percentage was down to them receiving the overtime ball first more often.

So the next step was to see how teams fared when they received the kick off in OT.In this instance pregame favourites were indeed slightly more luckier than their underdog counterparts.Just over 51% of the coin tosses were won by the pregame favourite.

Now if overtime should be considered a 50/50 proposition between the two teams prior to the overtime coin toss,there should be little or no difference between the winning percentages of favourites who receive the ball first in overtime and underdogs who also get the ball first.Every receiving team in overtime should just have the advantage of having the ball first,their pregame chances should count for nothing.

However the results don't support this view.

When the pre game favourite receives the kickoff in overtime they go onto win over 66% of the time.When the underdog receives they win just 50% of the time.

So it would seem that favourites win significantly more overtime games than do underdogs,even when you correct for favourites having a slightly better record at guessing the coin toss.Pre game match probabilities are  better indicators of what will happen in overtime compared to using what has already occurred.Favourites who are tied at the half still go onto win that tied game much more often than do their underdog opponents.Therefore it would be surprising if favs didn't continue the trend when they are taken to OT.

To summarise.
The receiving team has won 58% of overtime games since 1994.
When the receiving team is also the pregame favourite,they win 66% of the games.
When the receiving team is also the pregame underdog,they win 50% of the games.

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