like night and day
From 1988 to 2005, 8,093 batters were hit by pitches in day games in the Major Leagues, and 16,391 batters were hit by pitches in night games. But, there were 27,421 night games compared to only 12,952 day games, which means that while 67.9% of major league games were played at night, only 66.9% of plunks were recorded at night. The rate of plunks per plate appearance has been 4% higher during day games than night games, with an average of 8.1 plunks per 1000 plate appearances in the day games and 7.8 plunks per 1000 plate appearances in night games.
Over that same time span (through last season) Craig Biggio was hit by pitches 29% more frequently in day games than in night games. Biggio's averages were 28.8 plunks per 1000 plate appearances during the day, and 22.3 plunks per 1000 plate appearances in night games. This season, he's been hit 4 times during the day and 4 at night bringing his career totals to 94 day game plunks and 187 night game plunks. In 2006, he's been hit just once per 114.5 plate appearances in night games - about 3 times less frequently than his career average. In day games though, he's been hit 4 times in just 95 plate appearances - up 46% from his prior career average. Clearly this illustrates a major flaw in the Astros managerial strategy in 2006 - by resting Biggio during day games this season they've taken away his most plunk-productive plate appearances. Prior to this season he averaged 173 plate appearances per year in day games, but this year he's only had 95.
Another conclusion you might have drawn from Biggio's increased rate of being plunked in day games vs night games is that it might explain why Biggio's most plunk-productive days of the week are Saturday and Sunday, since there are more day games on the weekend than during the week. But, the stats don't quite show that. Saturday games have seen Biggio get hit 32 times at night and 19 during the day (through '05). Looking at night games alone, Biggio's plunks per 1000 plate appearances are still higher on Saturday than any day of the week. Day games on Sundays have been good for plunk progress, but among day games alone, Sunday's are the second least productive in terms of plunks per 1000 plate appearance - second only to Friday. Biggio has never been hit by a pitch during a day game on a Friday (88 plate appearances).
Craig Biggio's HBPs and plunks per 1000 plate appearances split by day of the week, and day vs night (through 2005):
|HBP||per 1000 PA||HBP||per 1000 PA||HBP||per 1000 PA|