from Amazon
Friday, June 24, 2011
Platoon advantage by time of day
Results indicate that players who were “morning types” had a higher batting average (.267) than players who were “evening types” (.259) in early games that started before 2 p.m. However, evening types had a higher batting average (.261) than morning types (.252) in mid-day games that started between 2 p.m. and 7:59 p.m. This advantage for evening types persisted and was strongest in late games that began at 8 p.m. or later, when evening types had a .306 batting average and morning types maintained a .252 average.
“Our data, though not statistically significant due to low subject numbers, clearly shows a trend toward morning-type batters hitting progressively worse as the day becomes later, and the evening-types showing the opposite trend,” said principal investigator and lead author Dr. W. Christopher Winter, medical director of the Martha Jefferson Hospital Sleep Medicine Center in Charlottesville, Va.
...but obviously the sample size is so tiny, that the “though not statistically significant” can’t just be walked by.
This is their sample size:
Nine participants were found to be evening types, and seven were morning types. Both groups had a mean age of 29 years. The study used the players’ statistics from the 2009 and 2010 seasons, which allowed for the analysis of 2,149 innings from early games, 4,550 innings from mid-day games and 750 innings from late games.
Reporting the innings played inflates the impact of the size of the sample, given that they are reporting batting averages (which means the opportunities is at bats, not innings). So, 2149 innings is like 1000 at bats, and 750 innings is like 350 at bats. Laughably small numbers of course. And next time, please, don’t use batting average. Linear Weights or wOBA would have been the far better choice.
However, I very much like the idea, and the effort. So, as a starting point, it’s great.
Glove-slap: Sky.
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