Monday, June 23, 2008

Do teams play worse after a time zone change? Part III

(UPDATE: This post was updated after I discovered my own analysis had three teams in the wrong time zones.)

In the last two posts, I reviewed reports of Dr. W. Christopher Winter's study on jet lag and baseball performance. The data suggested that the observed effect was just home field advantage.

In a comment to the second post, Dr. Winter said that most of the effect came from 2- and 3-hour time changes. So I reran the numbers, and considered only the first game where one team had 3-hour jet lag (from the day before), and the other team had none.

1997-2006 home winning percentage
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Home team jet-lagged: 14-19 (.424)
Road team jet-lagged: 72-46 (.610)


There's actually something here, although it's not statistically significant with the small sample of games.


Here are the breakdowns by decade:


2000-2007 home winning percentage
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Home team jet-lagged: 6-16 (.273)
Road team jet-lagged: 68-43 (.613)


1990-1999 home winning percentage
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Home team jet-lagged: 20-17 (.541)
Road team jet-lagged: 68-45 (.602)


1980-1989 home winning percentage
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Home team jet-lagged: 11-15 (.423)
Road team jet-lagged: 43-43 (.500)


1970-1979 home winning percentage
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Home team jet-lagged: 14-9 (.609)
Road team jet-lagged: 47-48 (.495)


None of these results looks statistically significant. The overall totals are:

1970-2007 home winning percentage
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Home team jet-lagged: 51-57 (.472)
Road team jet-lagged: 226-179 (.558)

The effect goes in the right direction, but neither result is significantly different from .530. The difference between the two numbers is 86 points; that's about 1.5 SD from zero, which again is not statistically significant.



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