Learn how probability, math, and statistics can be used to help baseball, football and basketball teams improve, player and lineup selection as well as in game strategy.

Loading...

From the course by University of Houston System

Math behind Moneyball

31 ratings

Learn how probability, math, and statistics can be used to help baseball, football and basketball teams improve, player and lineup selection as well as in game strategy.

From the lesson

Module 4

You will learn how to evaluate baseball fielding, baseball pitchers, and evaluate in game baseball decision-making. The math behind WAR (Wins above Replacement) and Park Factors will also be discussed. Modern developments such as infield shifts and pitch framing will also be discussed.

- Professor Wayne WinstonVisiting Professor

Bauer College of Business

[COUGH] Excuse me. In this video,

we're going to talk about evaluating field [INAUDIBLE] of baseball.

So we'll begin by talking about Bill James's idea of range factor.

Okay, so I think baseball started in 1869.

And basically, if you want to know what made a good fielder, when I was growing up

as a kid in the 50s and the 60s we would look at fielding percentage.

So in other words, if there's 100 balls for

a shortstop you had a chance of fielding.

And 98 you field okay and

two were errors.

You look at what percentage of those balls you had a shot at that you

fielded acceptably.

That'd be 98 divided by 100, or they would

do it as a 3 decimal, 0.98 fielding percentage.

Okay?

And so that's how fielders were rated for a long time.

Now this is a lesson for whatever business you're in, okay?

Bad metrics can be worse than no metric at all.

And fielding percentage is a bad metric, but for over 100 years,

nobody questioned it and nobody came up with anything else.

So Bill James, who again is a genius who may not know advanced math, but

basically we talked about Bill with runs created.

But in 1997 I believe, he thought about fielding.

And he said gosh, you look at fielding percentage.

It doesn't make that much sense to evaluate fielders by fielding percentage.

Consider a short stop, okay?

So his fielding percentage, based on the 100 balls he had a chance at.

Well if he never moved, balls are to the left of him,

balls are to the right of him, and basically those become hits, which really

hurt the pitcher's earn run average, and certainly hurt the team's win loss record.

So Bill James said, how can I come up with a better measure for

how good a fielder is and we'll focus on short stops here in this [INAUDIBLE].

Well Bill James came up with range factor.

So what you had in the box score for, I'm not sure if you had these in 1869,

but for a long long time, you have assists.

Let's say for short stops which is when usually when they catch a ground ball,

they throw it to second base for a force out or throw to first base.

Or maybe the second base man, well, or they maybe throw a guy out at the plate.

And then there's putouts, which maybe they make the pivot on the double play or

they catch a flyball.

But you've got assists, and you've got putouts.

So if you think about it, in the context of Bill James

was thinking about it, if I have a lot of assists and a lot of put outs,

that means I got to a lot of balls.

That's really, really good.

So that's the genesis of range factor.

So the range factor is basically you take assists plus put outs per inning,

and divide by the average, let's say for short stop.

And divide by the average

assists plus putouts per.

And if that number is bigger than one,

then your short stop sort of got to a lot more balls.

And if that Range Factor's less than one,

that ratio, he got to fewer balls than average.

Okay, and so where this really became a hot topic was Derek Jeter.

Great guy, Hall of Famer no doubt, great leader for

the Yankees, almost married Minka Kelly from Friday Night Lights.

He must have been doing something right.

But basically Bill James, and he won several Gold Gloves,

which was the award given to the best fielder.

And Bill James said I don't think Derek Jeter's that good a fielder.

And I really think you have to agree with Bill James on this.

You may not agree with him on everything.

So if you look at shortstops, so the average per game,

let's say assists plus put outs, let's abbreviate it is 4.48.

Okay.

And if you look at Derek Jeter throughout his career.

The assists plus put outs per game for

Derek Jeter for nine innings is 4.04.

That's about ten percent less than average.

Or if you work this out His range factor would sort of be about 90%.

It's about ten percent less balls than a average short stop.

Now how do you translate that to runs?

We'll get to that, we'll talk about ultimate zone rating and

plus minus systems in the next video.

Okay, and

then who's considered generally the greatest fielding short stop of all time?

I think it's Ozzie Smith of the Cardinals, the Wizard of Oz.

He just was amazing.

He could get to just about everything, throw runners out from deep in the hole.

And if you look at his assist plus putouts for the career,

You would get 5.23.

So, his range factor would be 5.23 divided by 4.48.

Which is about 1.17.

Which is much bigger, and

basically more above average than Derek Jeter's was below average.

And this passes the smelt test, because I think most people would agree Ozzy Smith

had great range, and Derek Jeter didn't have great range.

So now the question is, is this really a great metric for evaluating fielders?

Well it's been proved on a lot and what are some problems with range factor.

If your pitchers strike out a lot of batters, you're

not going to be able to get many assisted put outs, you gotta adjust for that.

If your pitchers throw fly balls or

ground balls, if you look at flyball to ground ball ratio,

then the short stop is not going to get a really good range factor.

You have to look at left-handed hitters and right-handed hitters.

So if you're going mainly against left-handed hitters,

they don't hit the ball much to short-stop.

And then you have to look at the park you play in.

Talk more about he effect of parks on baseball statistics later in the course.

But the parks should affect maybe the number of groundballs

that the shortstop has a chance of getting.

So there are adjusted range factors and stuff like that.

But that's way beyond the scope of where we're going.

But the brilliance of Bill James shines through again.

Using really middle school or grade school arithmetic, he came out with a way using

data that was already there to really show that for instance, Ozzie Smith was

a much better fielder than Derek Jeter, even if Ozzie Smith made more errors.

Now the trick is how can we translate this into runs, and

maybe get a better idea of how good a fielder, a player in any position is, and

we'll see how that works in the next video.

Coursera provides universal access to the world’s best education,
partnering with top universities and organizations to offer courses online.