FanPost

Adjusted Point Differential and Pythagorean Wins

More terrific statistical work from Citizen BelgianClipper, who apparently has a little too much time on his hands and some truly mad Excel skillz. Dude, step away from the keyboard. Maybe go see the sights. I hear the canals in Bruges are nice. Steve

Fellow citizens,

This is a follow-up fanpost on this fanshot which Steve so graciously promoted to the front page (thanks) - (you're welcome).

First off, I'm adding the Adjusted Point Differential for all NBA teams. I have also added this to the original fanshot but some of you might not have seen so:

Adjpexp_medium

How to read this

the 76ers have a actual point difference of 9.11 but the average team would be expected to have a point diff of 1.41 against their opponents. Thus their adjusted point difference is 7.70. The last 2 stats are the difference between their actual points and points expected for and against. This has the nice effect of dividing the Adjusted Point differential between offence and defence. Thus the Sixers have an Adjusted Point Diff of 7.70 which is composed of 2.11 points of offence and 5.59 on defence.

Secondly, Citizen Bandany wondered how this would effect Pythagorean Wins.

I'm using Basketball-reference.com method to expand this topic

W PythPythagorean Wins; the formula is G * (Tm PTS14 / (Tm PTS14 + Opp PTS14)). The formula was obtained by fitting a logistic regression model with log(Tm PTS / Opp PTS) as the explanatory variable.

this leads to the next table

Adjpexppyth1_medium

Act pyth is the Pythagorean Wins calculated using the actual point difference. Act/exp pyth is the Pythagorean Wins calculated by dividing the the actual point per game for and against by the respective expected values. Using this measure you get a corrected Pythagorean Wins which takes in account the strength of the opposition. If we compare both calculations you see that the Clips would be expected to have won 0.807 games more if we use this last calculation. the last 2 columns compare these calculations with the actual number of wins. it is a bit weird that the Clips get harped because of their point differential whilst OKC, even without adjustments, have by far the greatest difference between their actual wins and Pythagorean Wins.

Adjpexppyth3_medium

Well now I went completely mad: using the expected points values I calculated the Pythagorean Wins the average team would have against the opposition each team faced (exp pyth). In golf terms: par for the course. Then I compared them to the actual wins and the adjusted Pythagorean Wins. To counteract the difference in number of games I divided those comparisons by the number of games each team has played. "W vs exp pyth" per game essentially gives an indication by how much a team exceeds their expected Pythagorean Wins. "Act/exp vs exp" compares the adjusted Pythagorean Wins against the expected Pythagorean Wins. This could be seen as some sort of "objective" evaluation of a team results. The "mean" in the regression to the mean idea.

X
Log In Sign Up

forgot?
Log In Sign Up

Please choose a new SB Nation username and password

As part of the new SB Nation launch, prior users will need to choose a permanent username, along with a new password.

Your username will be used to login to SB Nation going forward.

I already have a Vox Media account!

Verify Vox Media account

Please login to your Vox Media account. This account will be linked to your previously existing Eater account.

Please choose a new SB Nation username and password

As part of the new SB Nation launch, prior MT authors will need to choose a new username and password.

Your username will be used to login to SB Nation going forward.

Forgot password?

We'll email you a reset link.

If you signed up using a 3rd party account like Facebook or Twitter, please login with it instead.

Forgot password?

Try another email?

Almost done,

By becoming a registered user, you are also agreeing to our Terms and confirming that you have read our Privacy Policy.

Join Clips Nation

You must be a member of Clips Nation to participate.

We have our own Community Guidelines at Clips Nation. You should read them.

Join Clips Nation

You must be a member of Clips Nation to participate.

We have our own Community Guidelines at Clips Nation. You should read them.

Spinner.vc97ec6e

Authenticating

Great!

Choose an available username to complete sign up.

In order to provide our users with a better overall experience, we ask for more information from Facebook when using it to login so that we can learn more about our audience and provide you with the best possible experience. We do not store specific user data and the sharing of it is not required to login with Facebook.

tracking_pixel_9347_tracker