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Tangotiger Blog

A blog about baseball, hockey, life, and whatever else there is.

Monday, April 07, 2014

Predictions Basics

There has got to be millions of people who  have this question every day, in their daily lives, whether it includes sports or not.

The same goes for division forecasts. From 1999 to 2012, an average of 11 MLB teams per season moved zero spots within their division, 10 moved a single spot, six moved two spots, two moved three spots and one moved four spots. But if we tried to parcel out specific teams into each category, the odds are we’d be less accurate than if we just predicted no movement for any team.

...

A No. 12 seed has won roughly 1.5 times in the round of 64 in each tournament since the NCAA field expanded to 64 teams in 1985. But if we took the most likely No. 12 vs. No. 5 upset in the field (according to the teams’ pre-tournament Simple Ratings) and flipped a coin over whether to pick the second-most likely upset, we’d pick winners at a rate 9 percent lower than if we just picked the No. 5 seed to win no matter what.

If you want to try something yourself, do this.  Roll a single dice (*)?.  You get an X if you roll a 1-4.  You get a Y if you roll 5 or 6.  What I'd like you to do is predict whether you will get an X or Y before your roll.  Then, record the result of your roll.  Do this, oh, 30 times.  (a) How many times were you right?

(*) Dice, not die.

Now, (b) how many times would you have been right if you simply predicted "X" each and every time?

***

Mathematically, the answers are: (a) 55.56% and (b) 66.67%

To figure out (a): of the two-thirds of the time that "X" pops, you will have guessed correctly 66.7% of the time; of the one-third of the time that "Y" pops, you will have guessed correctly 33.3% of the time.  So, (2/3)^2 + (1/3)^2 = 5/9

 

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April 07, 2014
Predictions Basics