Quick Workers and Human Rain Delays Followup

My column this morning on Baseball Prospectus is a follow up to a post last week on fast and slow workers. Specifically, I was interested in the question of whether pitchers who work more quickly reduce the number of errors committed behind them as the common wisdom would indicate.

Although it's difficult to identify quantitatively which pitchers are sloths (the slow ones like Steve Trachsel) and which are humingbirds (faster workers like Bob Gibson) my attempt using anecdotal evidence couldn't find any statistically significant difference between two groups of 10 pitchers encompassing over 40,000 innings pitched since 1970. At first glance it was the sloths who seemed to suppress the number of errors. However, pitchers who worked faster in my sample were more likely to be ground ball pitchers and so that fact had to be corrected for since groundballs are more likely to produce errors than fly balls or line drives. I also used a subset of the two groups whose performance was almost equivalent to remove the bias that good pitchers introduce by being able to suppress errrors and unearned runs.