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From: abgamble@water.UUCP (abgamble)
Newsgroups: net.sport.baseball
Subject: Re: World Series Probabilities
Message-ID: <843@water.UUCP>
Date: Sun, 22-Sep-85 14:48:12 EDT
Article-I.D.: water.843
Posted: Sun Sep 22 14:48:12 1985
Date-Received: Mon, 23-Sep-85 00:44:21 EDT
References: <538@lasspvax.UUCP>
Distribution: net
Organization: U of Waterloo, Ontario
Lines: 54

> In preparing a text on probability for nonscientists, a professor of ours
> considered the possibility that the teams were equally likely to win, and 
> computed the probabilities that the Series would go 4, 5, 6 or 7 games based
> on this assumption.  

> Using the above assumption, the chance of a Series of a given length can be
> calculated; comparing with data from 1926-1975, we find
> 
>        		1926-50		Calculation	1951-1975
> 7-games		   7		   7.8		   15
> 6-games		   5		   7.8		    3
> 5-games		   7		   6.2		    4
> 4-games		   6		   3.1		    3
> 
> The 15 7 game Series lies more than 3 standard deviations away, and the 3
> 6 game Series is over 2 standard deviations away.
> 
> To explain this anomaly we decided to test the assumption that the home team
> advantage was the cause.   
>          ...  In the last 30 years, the team which started the Series at
> home went on to win it 21 times ...
>                                           ... this 21/30 ratio
> corresponds to a .87 probability of winning a home game.
> 
> We don't have statistics for individual games; this should be checked
> by those who can and are interested.  Any other information relating
> to these issues would be appreciated.
> 
> 		Dan Rokhsar
> 		Eric Grannan

Between 1951 and 1975 there were 155 World Series games played. The
home team won 89 (57%) of those games, far short of the 87% you guessed.

I think a far more plausible explanation for all the long series, is
pitching. The strength of a team (the probability they will win) varies
a great deal depending on who their starting pitcher is. For an extreme
example, see the 1972 Phillies. Thus if you have one "hot" starter, you
may have an 70% chance of winning game 1, but only a 30% chance of
winning game 2.

More examples,
 - In the 1975 W.S., the Red Sox were 3-0 when Luis Tiant started, and
   0-4 in the other games.

 - During the 1960's, St. Louis was involved in the W.S. three times. The 
   Cardinals were 7-2 in games Bob Gibson started, and 4-8 otherwise.

Whether or not this explains the large number of 7-game series, I don't
know, but at the very least I think it's an important point you've
overlooked.
-- 

                           Bruce Gamble  -  abgamble@water.UUCP