When Is A Small Sample Size No Longer Small?
Eric Seidman at Fangraphs has a nice article summarizing research on when sample sizes become (somewhat) reliable for hitters. The research suggests that the following stats begin to stabilize with the corresponding number of plate appearances:
50 PA: Swing %
100 PA: Contact Rate
150 PA: Strikeout Rate, Line Drive Rate, Pitches/PA
200 PA: Walk Rate, Groundball Rate, GB/FB
250 PA: Flyball Rate
300 PA: Home Run Rate, HR/FB
500 PA: OBP, SLG, OPS, 1B Rate, Popup Rate
550 PA: ISO
Did not stabilize by 650 PA (the cutoff): BA, BABIP
The underlying work was done by a well respected analyst who goes by the handle Pizza Cutter at the Statistically Speaking blog. His research on pitchers is here.
6 months ago
Gopherballs
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Pizza Cutter is awesome
I'm not a sabermetrician, but I do play one at Driveline Mechanics.
by devil_fingers on May 22, 2009 11:46 AM EDT reply actions 0 recs
agreed, it's so hard to use just a knife and fork
hand gets all kinds of cheese and sauce all over it.
by benfunke on May 22, 2009 12:14 PM EDT up reply actions 0 recs
This is actually all really good information for fans
And the underlying support for the numbers is quite sound imo.
by ZeppelinDZ on May 22, 2009 12:43 PM EDT reply actions 0 recs
I dunno
Pizza Cutter isn’t his real name, he doesn’t have press credientials, and he’s probably never been in the clubhouse.
nor am I aware of any baseball teams that have asked him to be the manager, and there are thirty (holding up three fingers) of them.
Absolutely no credibility.
I'm not a sabermetrician, but I do play one at Driveline Mechanics.
by devil_fingers on May 22, 2009 12:53 PM EDT up reply actions 0 recs
Actually, Pizza Cutter turned down the D'Backs before they gave the job to former Royal A.J. Hinch
And one point to emphasize is that the articles suggest that those stats start to stabilize at those number of plate appearances, not that they become conclusively reliable at that point.
by Gopherballs on May 22, 2009 1:04 PM EDT up reply actions 0 recs
"Colonel Brett, did you order Farnsworth into the game against Thome?!?!?!"
“YOU’RE GODDAMNED RIGHT I DID!!!”
"Now…put that in your [BLEEP]ing pipe and smoke it." -Hal McRae
"I was doing this when BJ was in his father's nutsack." -Renzo Gracie
by Sweep_the_Leg on May 22, 2009 3:04 PM EDT up reply actions 0 recs
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