When Small Sample Isn’t Too Small Anymore
I’m sure you’re tired of hearing about exercising patience with your players. You want to know when their performance starts to mean something. Pizza Cutter @ Statistically Speaking, wanted to the know the same thing. He crunched the numbers, and here’s what he found:
These are the PA levels–at which, the players’ performance–can tell us about their skill going forward:
- 50 PA - swing percentage
- 100 PA - contact rate
- 150 PA - K rate, line drive rate, pitches/PA
- 200 PA - BB rate, grounder rate, GB/FB ratio
- 250 PA - flyball rate
- 300 PA - HR rate, HR/FB
- 350 PA - sensitivity
- 400 PA - none
- 450 PA -none
- 500 PA - OBP, SLG, OPS, 1B rate, popup rate
- 550 PA - ISO
- 600 PA - none
- 650 PA - none
- So after 100 PA (roughly a month, if a player is starting nearly everyday), I can tell you about how much a batter likes to swing and how good he is at making contact.
- At 150 PA I can tell you if [the batter] likes to hit line drives (and line drives are good…)
- At 150 PA, I can also start telling whether [the batter] likes to work the count and whether he’s a strikeout king.
- By 250 PA, I can tell a lot about his walking tendencies and what he’s going to be a ground ball hitter or a flyball hitter.
- At 300 PA, I finally find out whether or not the player likes to hit the ball out of the park every once in a while.
- Finally, a lot of the usual 1-number stats (OBP, SLG, OPS) don’t stablize until 500 PA, as well as knowing whether you’re a singles hitter.
Lets take a look at what Pizza Cutter found out about pitcher sample sizes:
- 50 BF - nothing
- 100 BF - nothing
- 150 BF - K/PA, grounder rate, line drive rate
- 200 BF - flyball rate, GB/FB
- 250 BF - nothing
- 300 BF - nothing
- 350 BF - nothing
- 400 BF - nothing
- 450 BF - nothing
- 500 BF - K/BB, pop up rate
- 550 BF - BB/PA
- 600 BF - nothing
- 650 BF - nothing
- 700 BF - nothing
- 750 BF - nothing
You can’t tell a lot about a pitcher by looking at his stats over a single season. You can get a pretty good idea of how often he walks and strikes batters out, and what type of batted balls he gives up generally… but that’s about it.
I cut out highlights that I felt would be most relevant to you. I’d highly advise you to read the rest of the study here: (Pitching & Batting).
If you need a good read on what a player will do this far in, perhaps look at his last 100/200/500 whatever PA’s. Or look at what he did last year. That’s going to be your best bet.
I will be refering back to it as I look for players to pickup.