Ripp wrote:Focus on the equation for the PDSS based DRat. You have a first term that is the same for every player on a team. You have a second term that is a function of Stop% (among other variables), and thus varies from player to player.
As I stated, both of these Oliver DRats involve adding a TEAM DRat number to some other number (the second term in your equation, I don't want to c/p it again) that corresponds solely to that only of an individual. Like, if you want to compute this PDSS Drtg number, you first compute Stop% for Amir, then one for Jose Calderon. If Amir's Stop% is 100%, this second term will be a big negative number (say, -8 or -9.) If Jose's were say 0%, this second term is a big positive number (say +8 or +9.)
Yet depending on the overall average defensive performance of the Raps, the Drtgs for both players might be very high.
My point is that this second term has a pretty natural interpretation as how a player impacts his team defense (either he improves it or worsens it.) But if I understand you correctly, it isn't important if he improves or worsens the defense, but what the final defensive number is? Or am I misunderstanding you?
Yet again, we're into basic mistakes of fact and my credulity strains under this weight.
The second term in both possessions is "DPoss%" - the amount of defensive possessions that a player bears individually when he's on the floor. In the estimated DRat, it's set as a default to .2 (1 ball / 5 players on the floor = .2). Why? Because we don't have any boxscore defensive data other than blocks, steals, rebounds and we can guess at the impact of fouls. That's all it is. I've explained the formula already. If a player's stop% is 1.000, his DPoss% could be .050, it could be .100, it could be .200, it could be .500, it could be 1.000 - they're completely unrelated. Nice try, though.
Err, but what people usually do is to compile raw counting stats like assists, blocks, rebounds, etc. You instead are not presenting the raw counting stats you kept track of, but a formula involving your new counting stats. Just because I think assists are reliable in the NBA doesn't mean I necessarily think PER is reliable, or WS, or WP, etc.
You were questioning the difficulties of tabulating the data (FM, FGA, FTO, FFT, FFTM) - no? It's no more subjective or fraught with difficulty than tabulating assists, and the information you get from that data is no more fraught with difficulty than, say, AST%.
Like I said earlier, I like the raw counting stats you kept, but don't have much personal confidence in this particular statistic involving those raw counting stats.
That's because you have chosen to adopt a hermeneutic of suspicion. I can't help you, there.
The 6 or 7 guys who lead a team in minutes played almost certainly consume most of the defensive and offensive possessions. If those 6 or 7 guys all have their Ortgs much higher than Drtgs, and the team has a bad Ortg/Drtg differential (and thus not very many wins), then something is wrong. Saying that some guys who aren't playing very many minutes are the ones chewing up all the possessions is not a good explanation for this discrepancy (think about what this means...you have guys playing no minutes Think at a very intuitive level about what you are saying. We have a team where the top 6 or 7 guys in minutes played ALL of an Ortg much higher than their Drtgs. These are the top dogs on the team, the guys leading the team in minutes played.
Yet the overall team as a whole has an Ortg less than the Drtg...substantially so, in fact. And you are saying that this is fine, because if we weighted instead by usage, then it would normalize out?
Not true. And this is where you're falling apart. You don't understand what an "individual possession" is in Oliver's systems: you're making basic mistakes of fact. I keep pointing them out, and you keep refusing to listen. Bosh, for example, played more than 200 minutes fewer than Bargnani, yet had over 200 more individual possessions.
I'm not going to spend all day correcting mistakes when you refuse to give the answers the time of day. You don't pay any heed to what an individual possession is (hint: it's not just being on the floor while the team has a possession) and thus you can't just sum by minutes. You have to sum individual Points Produced (an Oliver series of metrics) and divide by Individual Possessions (another series of Oliver metrics). I've explained that once, you ignored it, I'm not going to waste valuable bandwidth by doing it again.
The top 6 or 7 guys in minutes played on a team will represent the lion's share of the possessions consumed. I'm more than familiar with the metrics...in fact, familiar enough with them that I can step back and see if they pass basic smell tests, and make intuitive sense
All evidence speaks to the contrary.
I understand that. But how do I go from these individual ORats to the team ORat? That is my point...ultimately, if we want to check that the model we've built works well, it sure would be nice if it matched what actual game results are (e.g., team Ortg, team Drtg, same quantities for lineups, and finally Wins and Losses.)
Already explained. Sum individual Points Produced and divide by Individual Possessions for the entire team and it's...team points / team possessions. Wow, they're the same (with small allowance made for rounding, of course)!
That is not how statistical methodology works. You justify different quantities you use, not say, "Well, what else would you use?" Ideally you justify it by showing that nothing else makes sense, and moreover there are independent ways to show that any other choice leads to a bad outcome. In practice, you find some sort of weaker justification. And if you cannot do this, then you say that the choice is a bit ad hoc and arbitrary.
Uh, yes it is. Just saying, "I don't buy that" doesn't invalidate a methodology, which you want to do. And the standards of doubt you apply to this methodology and give a wide and sweeping pass to on/off court and APM is laughable.
No. I don't trust or believe for example Berri's Wins Produced, because you cannot use it to predict what is going to happen in games. Things like PER and +/- based approaches can be...that is why I have confidence that they have some value.
No, you can't use PER to predict wins and neither can you use raw +/-. PER doesn't even handle a lot of data.
This is the point I'm making....if you have a formula and have some quantity that you cannot justify, then why can't someone else take your formula and change the value 10 in your formula to a billion, and claim his formula is better than yours? How do you show him that yours is right (or at least, better), and his is wrong?
Oh, so you're fully conversant in all the elements of the regressions done to come up with APM? You - yourself - can fully justify every last element of them? Or PER - and derivatives of it? If not, this is as much of a double standard as I've ever seen.
I never said Jose Calderon was the root of all defensive evil: I said he's the primary cause of our defensive badness with Andrea being a secondary cause, helped along by the fact that the team violated the John Wooden Rule and put itself in situation where it had three players (Bargnani, Turkoglu and Calderon) in the starting lineup almost always at a massive disadvantage for speed and quickness, and often four (DeRozan). Contrary to popular opinion, I do not think this is the only metric one can use to evaluate defense: it is the most transparent, most direct, and actually based on direct analysis, not guesswork. Further, I haven't had any interact with the fact that this metric fluctuated so much for all players depending upon whether Jose was hurt, starting or coming off the bench, and for a good portion of the season Bargnani was either a neutral or slightly positive presence...on/off court data cannot speak to the righthood or wronghood of that thesis.