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Wednesday, April 30, 2008
Why numbers are only one lens of your glasses
I posted this on a hockey list, so I’ll repost here. It applies to any sport.
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I agree that someone using solely numbers is only seeing half the picture. Why can I be so firm on this? Because performance numbers are nothing more than a sample of a player’s talent (based on specific conditions, of which we may or may not be able to identify).
More specifically, every sample has a margin of error. Just look at goalies. A goalie can face 30 shots a game for 50 games, and that’s 1500 shots. Sounds like alot, right? Well, 2 standard deviations is .015 goals per shot. This means that a true .900 save percentage goalie will perform, 95% of the time, between .885 and .915. At .885, you are on your way out of the league. At .915, you are the #1 goalie on the team.
You need to know the “tools” of the players, so that you can better identify the noise that accompanies all performance of every player in every sport in the world.
Unless you have a large enough sample, in a group of players that have a wide spread of talent.