John Erardi Gets It -- "Who's Counting"

[*BaseClogger*]

Covariance. The players who get on base a lot tend to be the guys who SLG a lot. That is to say that they overlap. When you just look at one when running a correlation between OBP and Runs, the effect of the other one is still there, but you aren't giving it any credit.

But if those two things correlate with each other (teams who get OBP tend to SLG more - or less - than teams who don't), and OBP and SLG do correlate, then you are still capturing a lot of the other one's effect even though you aren't measuring it directly. So if you want to look at them at the same time, you have to get rid of the part that overlaps or you'd count it twice.

Let's say:
- A vs C have a correlation of .7
- B vs C have a correlation of .5

If you look at A & B together, your correlation isn't going to be 1.2 (that's impossible!). Instead, you are going to have to divide up that overlap.

Let's say that you re-run your analysis look at A and B at the same time to try and predict C.
- A and B together vs C has a correlation of .8

However, when you run a multivariate regression, you also get regression coefficients. Essentially, these tell you the component pieces of that overall model correlation. The process of running the regression tells you were the overlap is and gets rid of it so that the pieces fit together squarely.

So your new overall correlation of .8 is explained by taking 3 parts of A to every 1 part of B. Tthat's not .6 correlation and .2 correlation, mind you. That is to say that a change in OBP has 3 times the effect on run scoring as a similarly scaled change in SLG.

I don't know if that's actually the right ratio for runs and slugging (I thought it was more like 1.5:1), but that's covariance in a nutshell.

I follow everything except the multivariat regression. How is that performed?

BTW-thanks

[Yachtzee]

If you are looking for an estimation for how many runs a player has "created", you should look at the equation for "runs created."

If you are looking for the value that a player brings to a ballclub, you should look at a number of statistics.

While that is true, I think looking at RC is a pretty good indicator. Statistics like RC and even Bill James' win shares are attempts to find out a player's true contribution to the things necessary for winning ballgames. They come about from the endeavors of people seeking to find the true value of a baseball player.

Yes, when looking for the value of a player, you should look at a number of statistics. However, teams have entered into quite a few bad contracts with players based on stats like BA, RBI and Win-Loss records. I don't know of any bad contracts that teams entered into because they said "Wow, that guy's Runs Created is off the charts!" As Steel said, BA has its uses. It's just not the primary indicator of offensive production that it has been held out to be.

[pahster]

I follow everything except the multivariant regression. How is that performed?

BTW-thanks

It's a bit complicated: http://en.wikipedia.org/wiki/Regression_analysis

Basically you build a statistical model that tries to explain the variance in a single numerical dependent variable (so runs, for example) based upon the variance in a number of independent variables (take your pick: singles, doubles, HRs, RC, AVG, OBP, SLG, OPS, whatever). Of course there has to be some logic to the variables you choose; you can't just toss everything in. You also must ensure that there isn't too much covariation among the independent variables or you're model will end up screwy. The results of a regression will tell you what effect (positive or negative) each independent variable exerts upon the dependent variable, the size of the effect, and whether the effect is significant or not.

[*BaseClogger*]

It's a bit complicated: http://en.wikipedia.org/wiki/Regression_analysis

Basically you build a statistical model that tries to explain the variance in a single numerical dependent variable (so runs, for example) based upon the variance in a number of independent variables (take your pick: singles, doubles, HRs, RC, AVG, OBP, SLG, OPS, whatever). Of course there has to be some logic to the variables you choose; you can't just toss everything in. You also must ensure that there isn't too much covariation among the independent variables or you're model will end up screwy. The results of a regression will tell you what effect (positive or negative) each independent variable exerts upon the dependent variable, the size of the effect, and whether the effect is significant or not.

And some sort of stats software is necessary? I checked and I don't think this is possible on my TI-83...

[RedsManRick]

I follow everything except the multivariat regression. How is that performed?

BTW-thanks

You can do it in excel as well. Under the Tools section, there should be a Data Analysis option which includes all sorts of analytical functions. You just want "regression".

Your Y-axis is your dependent variable (runs) and X-axis is your independent variables -- all of them.

No need to select any of the options. The results will come out in a new worksheet. You'll have all the results you need, including the coefficients.

The coefficients give you the basic formula for the line of best fit.

Y = (Coefficient1)X1 + (Coefficient2)X2... etc.

[pahster]

And some sort of stats software is necessary? I checked and I don't think this is possible on my TI-83...

A lot of people use Excel. I use Stata, SAS, SPSS, and R.

[SteelSD]

BTW, while this thread has continued to 33 pages, does anyone want to guess who currently leads the Reds in RBI?

[MWM]

BTW, while this thread has continued to 33 pages, does anyone want to guess who currently leads the Reds in RBI?

And who got the winning RBI tonight with a .... breace yourself.... a walk? Unreal how that happens.

[edabbs44]

BTW, while this thread has continued to 33 pages, does anyone want to guess who currently leads the Reds in RBI?

In the land of the blind, the one eyed man is king.

[pahster]

BTW, while this thread has continued to 33 pages, does anyone want to guess who currently leads the Reds in RBI?

Time to move him down to the 9-hole. :

[KronoRed]

Time to move him down to the 9-hole. :

That's where RBI guys go.

[MWM]

So walks in the run to win the game yesterday; hits a GW 3 run homer today. Now if we can just figure out a way for him to win the game on a strikeout tomorrow, it would complete the trifecta.

[jojo]

So walks in the run to win the game yesterday; hits a GW 3 run homer today. Now if we can just figure out a way for him to win the game on a strikeout tomorrow, it would complete the trifecta.

Bases loaded, score tied, bottom of the 9th, full count.....swings and misses....Martinez lets it go through his legs....Dunn to first...game over.