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Old 04-27-2022, 05:53 PM   #81
skyblade
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Quote:
Originally Posted by waterhead View Post
It's crazy. The individual +/- for games was as large as 20 or 30 points between certain players. But the overall yearly average is what I was interested in.
How confident are you that EvanMiya is wrong? They list it as +/- and don't indicate they make any adjustments. Gobearcats.com doesn't have a gamebook for every game (@Wichita State doesn't have one for example) so it's pretty much impossible to check at least without being during the season.

Game by game +/- has a large variance and isn't a particularly reliable stat.
But I do think +/- is good at picking up players who do more (or less) than the stats indicate once you get to a large enough sample size. I do think it's debate-able if a season is a large enough sample size, but I do tend to trust a seasons worth of sample. Over multiple seasons there's generally enough variation (a player improves, coaching change, teammate change etc..) that any stat becomes less reliable.

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Old 04-28-2022, 10:44 AM   #82
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Originally Posted by sedziobs View Post
In that Temple game I was referring to, DDJ had a +/- of -17 in the second half despite being the leading scorer.

The shot charts are great too.
That has nothing to do with +/-. DDJ could be our leader in every category. It all depends on who you're sharing court with. Realistically it's worthless unless you want grade top 2-3 usage players on team. I can not score or let my man score, if other guys around get beat more than they win my +/- go be same.
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Old 04-28-2022, 10:51 AM   #83
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That has nothing to do with +/-. DDJ could be our leader in every category. It all depends on who you're sharing court with. Realistically it's worthless unless you want grade top 2-3 usage players on team. I can not score or let my man score, if other guys around get beat more than they win my +/- go be same.
I agree. I think +/- is only useful to supplement individual performances that you observed. In this case Temple was attacking DDJ on almost every play down the stretch and I think it showed in his +/-. Even then it was more of a problem with our coaching than DDJ. But you can't just look at +/- and assume anything because each player is only 20% of the action on the court. There is way too much noise over the season. Using it to grade entire 5-man lineups might be more useful.
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Old 04-28-2022, 02:47 PM   #84
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I agree that +/- is best as a supplement, but I would argue that is true for pretty much all stats. I don't think it is worse than any other stat over the course of the season. Per game variance is high in almost every stat.

Over the course of the season luck should pretty much even out, so if a guys +/- is higher or lower than you'd expect it's a reason to look deeper into their play. Even over the course of the season it could be luck, but statistically it probably isn't. It's worth breaking down if it's just one or two outlier games or a trend, but that's hard to do with +/- because it is not very well tracked.

I think DDJ's +/- was low for two reasons on the season. One is that he was not very efficient on offense, he scored a lot but he also stalled the ball and took bad shots. The second is he is undersized on defense and teams took advantage of that. But as others have said it is team related, DDJ being undersized was part of the problem, but the bigger part was we were forced to put DDJ on bigger guards because we didn't have a better option.
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Old 04-28-2022, 03:50 PM   #85
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All stats are tools, and you have to understand what they are telling you. Some conclusions can be drawn from stats, but others can't. For instance, you say "he was not very efficient on offense, he scored a lot but he also stalled the ball and took bad shots." There are some testable claims in there that we can look to stats to draw conclusions. We can look to true shooting percentage to determine if he was "efficient on offense". We can look at pts/40 to determine if "he scored a lot". And we can look at his long 2 rate as one measure of "bad shots".

The problem with +/- is we don't have a specific question to answer. We're looking at broad qualities with many variables and trying to draw conclusions that aren't robust.

With any statistical analysis, not just in sports, predictive value is what is important. If a stat can't help make accurate predictions, it's not worth relying on. It might help create a narrative, but it won't help make rational decisions. I prefer to stick to stats that are predictive. OReb, Free Throw, and Block+Steal rates are all generally consistent from year to year, perhaps after adjusting for usage and competition. Players generally see improvements in TO and Foul rates as they progress.

TS%, DReb, and Assist rates fluctuate a lot and can go up or down. Those are much less predictive, but at least they answer a specific question about the current/previous year. I just don't see much value in +/- over the course of a season. It's an interesting stat, but I don't think it's very useful.
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Old 04-28-2022, 10:10 PM   #86
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Quote:
Originally Posted by skyblade View Post
How confident are you that EvanMiya is wrong? They list it as +/- and don't indicate they make any adjustments. Gobearcats.com doesn't have a gamebook for every game (@Wichita State doesn't have one for example) so it's pretty much impossible to check at least without being during the season.

Game by game +/- has a large variance and isn't a particularly reliable stat.
But I do think +/- is good at picking up players who do more (or less) than the stats indicate once you get to a large enough sample size. I do think it's debate-able if a season is a large enough sample size, but I do tend to trust a seasons worth of sample. Over multiple seasons there's generally enough variation (a player improves, coaching change, teammate change etc..) that any stat becomes less reliable.
Go Bearcats does have all the gamebooks. I was calculating up until about 6-8 games left in season. I am confident in what I calculated for actual.

I explained to Sedz how to find some of the missing game books but I was able to find everyone until I stopped doing it. I will let someone else confirm if my numbers were incorrect. I am not under the impression I donít make mistakes.

I am very confident Miyaís calculating is not actual plus minus. He describes how they do it on his site. Itís an algorithm. If it were not an algorithm it would just be simple addition and averages based on actual game plus minus numbers. Add plus minus and divide by number of games. Its not fancy
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Old 04-28-2022, 10:25 PM   #87
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Go Bearcats does have all the gamebooks. I was calculating up until about 6-8 games left in season. I am confident in what I calculated for actual.

I explained to Sedz how to find some of the missing game books but I was able to find everyone until I stopped doing it. I will let someone else confirm if my numbers were incorrect. I am not under the impression I donít make mistakes.

I am very confident Miyaís calculating is not actual plus minus. He describes how they do it on his site. Itís an algorithm. If it were not an algorithm it would just be simple addition and averages based on actual game plus minus numbers. Add plus minus and divide by number of games. Its not fancy
He describes his process as stats related. An adjusted BPM which is also an algorithm. Plus minus IS already THE stat if you are calculating it you divide by number of games.
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Old 04-28-2022, 10:28 PM   #88
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He describes his process as stats related. An adjusted BPM which is also an algorithm. Plus minus IS already THE stat if you are calculating it you divide by number of games.
By the way I donít place ANY emphasis on individual games or even short stretches. I only like plus minus over long term.
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Old 04-29-2022, 12:21 AM   #89
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Originally Posted by waterhead View Post
He describes his process as stats related. An adjusted BPM which is also an algorithm. Plus minus IS already THE stat if you are calculating it you divide by number of games.
He does have a "Box BPR" which is adjusted, but the "+/-" appears to be raw:
Quote:
+/-: Number of points scored for the player's team with him on the court, minus the number of points scored by the opponent with him on the court.
If you didn't do the whole season, I'm not sure how you could be confident his numbers are wrong. The only reason I can see that they might not be raw is he discounts possessions when the game is a blowout. It doesn't say if that's only for BPR or if it also affects the +/-.
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Old 04-29-2022, 01:30 AM   #90
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Originally Posted by sedziobs View Post
He does have a "Box BPR" which is adjusted, but the "+/-" appears to be raw:

If you didn't do the whole season, I'm not sure how you could be confident his numbers are wrong. The only reason I can see that they might not be raw is he discounts possessions when the game is a blowout. It doesn't say if that's only for BPR or if it also affects the +/-.
His numbers are going to be correct for whatever measures he is using. I donít think they are wrong. I am just saying itís not an actual plus minus number. Itís weighted somehow. Maybe itís weighed better idk. Itís just not actual
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