On Base Percentage vs. Slugging Percentage

A while back, I wrote a post about the importance of On Base Percentage (OBP) and Slugging Percentage (Slugging) to scoring runs. OBP measures how often players reach base safely on hits and walks, and slugging averages out a players total bases per at bat, giving more weight to extra base hits. People who have read Moneyball by Michael Lewis know that the Oakland “secret” was all about getting guys on base at a high rate, thus higher OBPs. I have also shown that the simple sum of these two stats – OBP and Slugging – into a stat called OPS has an exceptionally higher correlation to runs scored. But the question of which is more important, OBP or slugging, is a little trickier to pinpoint, until one clicks the “data analysis” button on Excel.

Multiple linear regression is a complex statistical…just kidding. Excel tells me this: based on the last 10 years of teams stats, OBP and Slugging alone are able to statistically explain about 90% of the variance in run scoring. (This is a pretty damn good figure to work with FYI.) An increase of about 28 OBP points (like 0.400 to 0.428) and 48 slugging points contributes to ONE extra run scored per game by a team. So does this mean that OBP is 1.7 times as important  as slugging (48/28)? Not exactly. Remember that OBP and Slugging share some stats: when a team gets any kind of hit, it is recorded both in the OBP and in the slugging, just in different ways. This means that OBP and Slugging have some correlation to each other.

Though not quite 1.7, OBP is sill about 1.2 times as important as Slugging. So even though OBP/Slugging splits of 350/550 and 450/450 produce the same OPS, it is likely that the 450/450 split will produce more runs.

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