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-   -   No bump up with 100% winning record? (http://tt.tennis-warehouse.com/showthread.php?t=446915)

robert 11-29-2012 03:51 PM

No bump up with 100% winning record?
 
This guy went 13-0 in singles this year. 7 of them are local playoff and Sectional. But no bump in the year end rating?

Also he bagled the opponents in Sectional matches. How is it possible?

NTRPolice 11-29-2012 04:31 PM

Sounds like me almost...

Even winning like that may not earn him enough points to move up. If I didnt play up this year, I wouldnt have moved up.

If this person was very low on the dynamic scale and his/her opponents were also low its quite possible there is no bump.

Also, not every league counts towards/against NTRP, and not every player at the playoff (benchmark) level is equivalent as the next.

Alchemy-Z 11-30-2012 03:24 AM

I've had team mates with losing records get bumped..but me and another team mate went undefeated for the season did not get bumped.

schmke 11-30-2012 05:37 AM

Quote:

Originally Posted by Alchemy-Z (Post 7039339)
I've had team mates with losing records get bumped..but me and another team mate went undefeated for the season did not get bumped.

Your specific won/lost record is meaningless when it comes to calculating your NTRP rating. Your rating is based solely on the game differential from the score of the match and the then current dynamic ratings of all the players involved.

If you play weak opponents, those rated in the lower end of your level or even players in a level lower that are playing up, and/or play with a very strong doubles partner, you can win all your matches and actually have your rating go down.

Conversely, if you play strong opponents, if perhaps you yourself are playing up, or play with a weak partner, you can lose a match and improve your rating.

And of course, because game differential is used, you can win a match 0-6,7-6,1-0 but actually be -4 on game differential which even against good competition could cause your rating to go down.

So it all depends on the specifics of every match and not your win/loss record.

Mauvaise 11-30-2012 05:51 AM

I think it can depend on who he is beating and by what scores, yes?

I know my friend only lost once at the 4.0 level in singles, and a lot of the time crushed his opponents 6-2, 6-1, etc. and he didn't get bumped up. But, those "crushings" were against 3.5C ranked guys, and he's expected to do that. Against 4.0C guys his scores were much more competitive (with 3rd set tie breaks thrown in).

LuckyR 11-30-2012 07:32 AM

Yet more evidence that a seriously flawed system will yield... flawed results. No suprise there.

schmke 11-30-2012 07:44 AM

Quote:

Originally Posted by LuckyR (Post 7039651)
Yet more evidence that a seriously flawed system will yield... flawed results. No suprise there.

How are any of the examples cited in this thread evidence of a flawed system or results? With the information provided, all we know is that a player won a lot and wasn't bumped and someone that didn't win a lot has been bumped. But we have no specifics and it has been described how that is possible and further it has been noted that in one case some of a 4.0's wins were over 3.5s playing up which the 4.0 is also supposed to win.

I'm not saying the NTRP system is perfect, it isn't. But IMHO, arguing that a good rating system has to move a player up simply because they win even if it is against weak competition shows a lack of understanding for rating systems.

ronray43 11-30-2012 07:56 AM

Typical NTRP paradox. What gets you to sectionals, districts, etc., is your win-loss record--period. Then, when it comes to NTRP, USTA says win-loss isn't important. Well, if win-loss isn't important to determining NTRP, then why is win-loss record the only thing that matters at the end of a season. You'd think they'd either incorporate some sort of win-loss algorithm into NTRP or determine who wins a particular match by who played better based on dynamic NTRP (i.e., if I'm supposed to lose 2-2 to a better player, but lose 3-3, then I get the match win, similar to a golf handicap match).

Regardless, until NTRP starts taking into account the most important item used to determine who advances in league play (win-loss record only), the system will remain flawed. In Colorado, we literally have a couple dozen folks who won all their league matches and didn't get moved up.

burosky 11-30-2012 08:02 AM

After reading accounts like these in what seems to be year after year, I am no longer surprised. I bet there are a lot more instances (even more extreme cases) that are just not mentioned here.

Maybe that would be a more interesting read. What is the most extreme case (bump up, bump down or no bump) that you know of?

schmke 11-30-2012 08:29 AM

Quote:

Originally Posted by ronray43 (Post 7039700)
You'd think they'd either incorporate some sort of win-loss algorithm into NTRP or determine who wins a particular match by who played better based on dynamic NTRP (i.e., if I'm supposed to lose 2-2 to a better player, but lose 3-3, then I get the match win, similar to a golf handicap match).

This expected result is in effect what the NTRP algorithm calculates and the result being better or worse than this cause one's rating to go up or down. So one could take this and determine "virtual wins" or come up with a handicapping system where a player gets 3 games per set or whatever is appropriate given the player's current ratings.

Being a ratings guy, this could be very interesting and a part of me would love to see it, but it would also change he dynamic of the game significantly, perhaps to its detriment. But on the surface, it would eliminate some of the ways one can win and advance but manipulate ones rating to avoid being bumped.

10sjunkie 11-30-2012 08:33 AM

"What gets you to sectionals, districts, etc., is your win-loss record--period."

What gets you there is your team's win/loss record, not your individual win/loss record. Your NTRP rating is your individual rating, not a team rating.

jmnk 11-30-2012 08:37 AM

Quote:

Originally Posted by LuckyR (Post 7039651)
Yet more evidence that a seriously flawed system will yield... flawed results. No suprise there.

how is it flawed? What is so hard to understand that beating players that are no better than you will not make you move up?
If your dynamic rating is 3.89 (so you are 4.0 player) and you beat a player with dynamic rating of 3.52 (so he is also 4.0) by a score of 6:4 7:6 - how is that supposed to mean you should move up? By NTPR formula, which is based on old and proven ELO rating designed originally for chess (and now used very widely in competition where you can't possibly play --all-- of the opponents: tennis, soccer, on-line games, etc), the expected result is likely around 6:2, 6:2 - so you did worse than expected, which means your ranking went down despite the win.
Now have it happened 15 times over the course of the season and your dynamic ranking (and therefore NTPR ranking at the end of the season) will really go down and not up.

Now, if you want to argue that in tennis we should not care about games won/lost but only about whether someone actually won a match - you may have an argument. Such a system will have its own set of problems, mainly that you will have only two outcomes of any match (a win or a loss) vs. a set of outcomes (depending on games won/lost difference) and therefore there will be way less data for algorithm to crunch. Not that such a system is unheard of - Rogers tennis ranking in Canada is based purely on win/loss (and the 'weight' of the match, some matches are treated more importantly than others). FIFA ranking (which is actually very similar) uses a hybrid method - it cares about both pure win/loss, but also takes into account goal differential (which is equivalent to games differential in tennis).

All of those WTF-like cited cases are likely outliers anyway. The system overall is pretty accurate and serves the purpose. plus it is easy to say 'flawed system' - why don't you propose a better one? I'm sure it will have many edge cases where it will seem illogical (to an untrained eye of course).

ronray43 11-30-2012 08:54 AM

Well, I guess what I'm really trying to get across is that win-loss record should count for at least part of one's NTRP rating.

For the folks in the middle of their rating, NTRP is probably just fine. However, for those near the very bottom (me, for example), according to NTRP, we're supposed to lose all our matches. And, when we do lose all our matches, year after year, NTRP is happy, because the actual result met the expected outcome. So, when the end of year ratings come out, we get to stay at the same rating, because we lost all our matches, just like the algorithm predicted, and, guess what, we get to lose all our matches the next year, 'cause that's how NTRP is structured.

Sure, we can all try to get better, but some of use are almost 60 years old, and we've gotten about as good as we can get. So, if NTRP would at least have some consideration for win-loss record, it would probably help those of use who are at the bottom of their rating level, and also help to move up the guys who win 90% of their matches year after years and stay at the same leve.

LuckyR 11-30-2012 08:57 AM

Quote:

Originally Posted by jmnk (Post 7039777)
how is it flawed? What is so hard to understand that beating players that are no better than you will not make you move up?
If your dynamic rating is 3.89 (so you are 4.0 player) and you beat a player with dynamic rating of 3.52 (so he is also 4.0) by a score of 6:4 7:6 - how is that supposed to mean you should move up? By NTPR formula, which is based on old and proven ELO rating designed originally for chess (and now used very widely in competition where you can't possibly play --all-- of the opponents: tennis, soccer, on-line games, etc), the expected result is likely around 6:2, 6:2 - so you did worse than expected, which means your ranking went down despite the win.

Now have it happened 15 times over the course of the season and your dynamic ranking (and therefore NTPR ranking at the end of the season) will really go down and not up.

Now, if you want to argue that in tennis we should not care about games won/lost but only about whether someone actually won a match - you may have an argument. Such a system will have its own set of problems, mainly that you will have only two outcomes of any match (a win or a loss) vs. a set of outcomes (depending on games won/lost difference) and therefore there will be way less data for algorithm to crunch.


Well, it flawed because, to use your (and the OP's) example the statistical chance that your example 3.89 player will meet only players of his or lower ranking 15 times in a row is less than 3 one thousanths of one percent.

In other words that reality exists only in strawman arguments like your post, not in the real world.

You scoff in your second bolded statement at the idea of W/L record being meaningful. My answer: if it works for Pros, why use a convoluted system for everyone else? If you lose in the first round of Wimbledon, it doesn't matter to your ATP points if it is to Fed or a Lucky Loser, you get the same credit.

dizzlmcwizzl 11-30-2012 09:27 AM

Quote:

Originally Posted by LuckyR (Post 7039815)
You scoff in your second bolded statement at the idea of W/L record being meaningful. My answer: if it works for Pros, why use a convoluted system for everyone else? If you lose in the first round of Wimbledon, it doesn't matter to your ATP points if it is to Fed or a Lucky Loser, you get the same credit.

Wins and losses are usually related to whom you get lined up against. The ratings systems should operate independently of whom the opposition lines up against you. Therefore if you only get to play weak competition in league, that is not really your fault but you can still dominate them and earn a bump. However, if you manage to win all of these matches against weak sisters, but only barely do so, then no bump for you. Contrast that with playing line 1 singles against only the stiffest competition and earning a record of 6-4. This might show that you are ready for the next level.

I am going to provide you with a real world example of why using wins / losses would cloud the ratings issue.

My 4.0 team has won districts and gone to sectionals 3 years in a row. We were very good relative to our peers. On this team we had 5 guys get bumped up this week. Each of these guys had solid successful seasons and their average record for our team was something like 10-4. This seems good, but not great ... however, once you consider that most of the losses came against other very good 4.0 players at sectionals the record seems a little more impressive.

Contrast that with 4 other guys on our roster that went undefeated this year. Their combined record for the season was something like 15-0. Not one of them got bumped, nor are they worthy of getting bumped. Why? Because we only let them play against the weak teams where we did not need the first team available to get the win.

jmnk 11-30-2012 09:35 AM

Quote:

Originally Posted by jmnk (Post 7039777)
how is it flawed? What is so hard to understand that beating players that are no better than you will not make you move up?
If your dynamic rating is 3.89 (so you are 4.0 player) and you beat a player with dynamic rating of 3.52 (so he is also 4.0) by a score of 6:4 7:6 - how is that supposed to mean you should move up? By NTPR formula, which is based on old and proven ELO rating designed originally for chess (and now used very widely in competition where you can't possibly play --all-- of the opponents: tennis, soccer, on-line games, etc), the expected result is likely around 6:2, 6:2 - so you did worse than expected, which means your ranking went down despite the win.
Now have it happened 15 times over the course of the season and your dynamic ranking (and therefore NTPR ranking at the end of the season) will really go down and not up.

Now, if you want to argue that in tennis we should not care about games won/lost but only about whether someone actually won a match - you may have an argument. Such a system will have its own set of problems, mainly that you will have only two outcomes of any match (a win or a loss) vs. a set of outcomes (depending on games won/lost difference) and therefore there will be way less data for algorithm to crunch. Not that such a system is unheard of - Rogers tennis ranking in Canada is based purely on win/loss (and the 'weight' of the match, some matches are treated more importantly than others). FIFA ranking (which is actually very similar) uses a hybrid method - it cares about both pure win/loss, but also takes into account goal differential (which is equivalent to games differential in tennis).

All of those WTF-like cited cases are likely outliers anyway. The system overall is pretty accurate and serves the purpose. plus it is easy to say 'flawed system' - why don't you propose a better one? I'm sure it will have many edge cases where it will seem illogical (to an untrained eye of course).

Quote:

Originally Posted by LuckyR (Post 7039815)
Well, it flawed because, to use your (and the OP's) example the statistical chance that your example 3.89 player will meet only players of his or lower ranking 15 times in a row is less than 3 one thousanths of one percent.

In other words that reality exists only in strawman arguments like your post, not in the real world.

Let's see. Assuming you play in 4.0 league, so you are going to play only 4.0 NTPR players (in fact, due to the fact people are allowed to play up, you may in fact play someone below 4.0, but --never-- above 4.0). Again assuming that all 4.0 players are uniformly distributed - i.e there's equal chance of your opponent having 3.52 dynamic ranking as someone having 3.97 (in short, meeting a player of any dynamic rating in 3.50-3.99 range is equally likely). If you ranking is 3.89, you have 78% chance of meeting someone with a lower dynamic ranking. ((3.89-3.5)/0.5). The chance of that happening 15 times in a row is actually ~0.024 - which is a bit over 2%. Not sure where you got your "less than 3 one thousanths of one percent." from??
Note, that both of the above assumptions made the result --smaller-- that what would have happened in real life. Since you actually --can-- play someone with DR less than 3.5, and in any range there are likely more players in the lower/mid part of the range than in the upper range - so again in reality you are more likely to meet someone with a lower ranking.

Quote:

Originally Posted by LuckyR (Post 7039815)
You scoff in your second bolded statement at the idea of W/L record being meaningful.

I do not scoff at the idea of using W/L record as being meaningful. I'm sorry if it appears so. I'm saying that using games difference for casual USTA play is 'more meaningful' than using just W/L results.

Quote:

Originally Posted by LuckyR (Post 7039815)
My answer: if it works for Pros, why use a convoluted system for everyone else? If you lose in the first round of Wimbledon, it doesn't matter to your ATP points if it is to Fed or a Lucky Loser, you get the same credit.

Because top PROs play around 75-100 matches a year so there's way more data sample with just W/L ratio. Those that lose early have only 30-50 matches, the data sample is small, that's why it can be easily argued that PROs in 150 - 300 range are pretty much all the same level and they move so much with each result. Look at Janowicz - he had essentially one excellent week and few so-so results, and he moved from outside 100 to 26 spot. While I like him a lot - you really think he improved so much?
In addition in ATP tournaments, the points you get depend on the round you won. You know why - because underlying assumption is that the deeper you advance the better players you meet, so your win is worth more. Of course it does not work all the time - but on average, over the course of the year, it works fine.
But that will not work for USTA league - because players simple do not play that much. And there's no 'going deeper' in the tournament, for those that do not advance to post-season play (which is a vast majority) all the matches are worth the same.

Again - please propose a system and we can take records of few players from USTA and I'm sure we will be able to show you that your system is equally, if not more, illogical.

LuckyR 11-30-2012 10:08 AM

Quote:

Originally Posted by jmnk (Post 7039861)
Let's see. Assuming you play in 4.0 league, so you are going to play only 4.0 NTPR players (in fact, due to the fact people are allowed to play up, you may in fact play someone below 4.0, but --never-- above 4.0). Again assuming that all 4.0 players are uniformly distributed - i.e there's equal chance of your opponent having 3.52 dynamic ranking as someone having 3.97 (in short, meeting a player of any dynamic rating in 3.50-3.99 range is equally likely). If you ranking is 3.89, you have 78% chance of meeting someone with a lower dynamic ranking. ((3.89-3.5)/0.5). The chance of that happening 15 times in a row is actually ~0.024 - which is a bit over 2%. Not sure where you got your "less than 3 one thousanths of one percent." from??
Note, that both of the above assumptions made the result --smaller-- that what would have happened in real life. Since you actually --can-- play someone with DR less than 3.5, and in any range there are likely more players in the lower/mid part of the range than in the upper range - so again in reality you are more likely to meet someone with a lower ranking.


I do not scoff at the idea of using W/L record as being meaningful. I'm sorry if it appears so. I'm saying that using games difference for casual USTA play is 'more meaningful' than using just W/L results.


Because top PROs play around 75-100 matches a year so there's way more data sample with just W/L ratio. Those that lose early have only 30-50 matches, the data sample is small, that's why it can be easily argued that PROs in 150 - 300 range are pretty much all the same level and they move so much with each result. Look at Janowicz - he had essentially one excellent week and few so-so results, and he moved from outside 100 to 26 spot. While I like him a lot - you really think he improved so much?
In addition in ATP tournaments, the points you get depend on the round you won. You know why - because underlying assumption is that the deeper you advance the better players you meet, so your win is worth more. Of course it does not work all the time - but on average, over the course of the year, it works fine.
But that will not work for USTA league - because players simple do not play that much. And there's no 'going deeper' in the tournament, for those that do not advance to post-season play (which is a vast majority) all the matches are worth the same.

Again - please propose a system and we can take records of few players from USTA and I'm sure we will be able to show you that your system is equally, if not more, illogical.

Perhaps you are unfamiliar with the term "sandbagger". I guess it is unknown in your league. Over here on planet Earth, folks are familiar with it. My numbers were assuming that someone with a slightly above halfway rating in the division (your example of 3.89) would likely have a 50:50 chance of playing someone worse rather than better (regardless of their "rating"). As you know .50 to the 15th is 3 to the -5th.

The USTA knows that their system is flawed by allowing sandbagging, hence their decision to preempt criticism of it by stating that 6-0, 6-0 is an expected score between players of the same rating. Huh?

Yes, if we used my proposal to use W/L to determine ranking, you are correct that somewhere between zero and 2 percent of the time it will get it wrong (in the scenario you used). But my experience is: I see way more than 2% of players in the current system at the wrong level.

jmnk 11-30-2012 10:44 AM

Quote:

Originally Posted by jmnk (Post 7039861)
Let's see. Assuming you play in 4.0 league, so you are going to play only 4.0 NTPR players (in fact, due to the fact people are allowed to play up, you may in fact play someone below 4.0, but --never-- above 4.0). Again assuming that all 4.0 players are uniformly distributed - i.e there's equal chance of your opponent having 3.52 dynamic ranking as someone having 3.97 (in short, meeting a player of any dynamic rating in 3.50-3.99 range is equally likely). If you ranking is 3.89, you have 78% chance of meeting someone with a lower dynamic ranking. ((3.89-3.5)/0.5). The chance of that happening 15 times in a row is actually ~0.024 - which is a bit over 2%. Not sure where you got your "less than 3 one thousanths of one percent." from??
Note, that both of the above assumptions made the result --smaller-- that what would have happened in real life. Since you actually --can-- play someone with DR less than 3.5, and in any range there are likely more players in the lower/mid part of the range than in the upper range - so again in reality you are more likely to meet someone with a lower ranking.


I do not scoff at the idea of using W/L record as being meaningful. I'm sorry if it appears so. I'm saying that using games difference for casual USTA play is 'more meaningful' than using just W/L results.


Because top PROs play around 75-100 matches a year so there's way more data sample with just W/L ratio. Those that lose early have only 30-50 matches, the data sample is small, that's why it can be easily argued that PROs in 150 - 300 range are pretty much all the same level and they move so much with each result. Look at Janowicz - he had essentially one excellent week and few so-so results, and he moved from outside 100 to 26 spot. While I like him a lot - you really think he improved so much?
In addition in ATP tournaments, the points you get depend on the round you won. You know why - because underlying assumption is that the deeper you advance the better players you meet, so your win is worth more. Of course it does not work all the time - but on average, over the course of the year, it works fine.
But that will not work for USTA league - because players simple do not play that much. And there's no 'going deeper' in the tournament, for those that do not advance to post-season play (which is a vast majority) all the matches are worth the same.

Again - please propose a system and we can take records of few players from USTA and I'm sure we will be able to show you that your system is equally, if not more, illogical.

Quote:

Originally Posted by LuckyR (Post 7039917)
Perhaps you are unfamiliar with the term "sandbagger". I guess it is unknown in your league. Over here on planet Earth, folks are familiar with it.

not sure what sandbagging has to do with this discussion. Are you suggesting that one cannot sandbag by outright losing the match rather than winning it closely? Could you kindly clarify what your point is?

Quote:

Originally Posted by LuckyR (Post 7039917)
My numbers were assuming that someone with a slightly above halfway rating in the division (your example of 3.89) would likely have a 50:50 chance of playing someone worse rather than better (regardless of their "rating"). As you know .50 to the 15th is 3 to the -5th.

I'm not sure why you think that 3.89 DR is 'slightly above' halfway ranking? Halfway is 3.75. 3.89 is way more that slightly above halfway. Also, next time you make an assumption that is not obvious to anyone but you yourself, please make it clear. Rather than, you know, implying that someone else does not know what 0.5^15 is.
But if you want to discuss a case where someone is indeed at the halfway point, at 3.75. in this case he needs to get his ranking up by .25 points to get bumped. It is significantly harder to earn this .25 dynamic ranking points. Someone who started at 3.89 needs only .11 to get bumped. It really all evens out - you start at the higher DR, you need to play better opponents to move your DR up, but you only need to move up by a small amount. You start at lower DR - it is easier to earn DR points (because you are more likely to meet higher ranked opponents more often) but you need to earn more of those DR points. the system actually makes it all take into consideration which makes it, I don't know, logical?

Quote:

Originally Posted by LuckyR (Post 7039917)
The USTA knows that their system is flawed by allowing sandbagging, hence their decision to preempt criticism of it by stating that 6-0, 6-0 is an expected score between players of the same rating. Huh?

could you elaborate on what you mean? the expected score takes into consideration dynamic rating, not your NTPR one.
There's no system in the world that would prevent sandbagging. None. Except having all players play in one single category. Do you really want that?

Quote:

Originally Posted by LuckyR (Post 7039917)
Yes, if we used my proposal to use W/L to determine ranking, you are correct that somewhere between zero and 2 percent of the time it will get it wrong (in the scenario you used). But my experience is: I see way more than 2% of players in the current system at the wrong level.

really. you are sure of that. how exactly? do you have some stats? data? dizzlmcwizzl gave you a perfect example of why going by W/L is no better.

If you go by W/L, and a player wants to get bumped - he just needs to play at #3 (assuming this is a 3 players team, singles only). He is likely to play weaker opponents. You are essentially saying that a player beating 3.60 DR players 10 times is vastly better (and should get moved up) than a player who plays 3.80 DR players and has 4/6 W/L ratio. really? that is logical?

(i do think that not separating doubles and singles as far as rating is concerned is the biggest flaw of the system).

beernutz 11-30-2012 11:03 AM

Quote:

Originally Posted by jmnk (Post 7039777)
how is it flawed? What is so hard to understand that beating players that are no better than you will not make you move up?
If your dynamic rating is 3.89 (so you are 4.0 player) and you beat a player with dynamic rating of 3.52 (so he is also 4.0) by a score of 6:4 7:6 - how is that supposed to mean you should move up? By NTPR formula, which is based on old and proven ELO rating designed originally for chess (and now used very widely in competition where you can't possibly play --all-- of the opponents: tennis, soccer, on-line games, etc), the expected result is likely around 6:2, 6:2 - so you did worse than expected, which means your ranking went down despite the win.
Now have it happened 15 times over the course of the season and your dynamic ranking (and therefore NTPR ranking at the end of the season) will really go down and not up.

Now, if you want to argue that in tennis we should not care about games won/lost but only about whether someone actually won a match - you may have an argument. Such a system will have its own set of problems, mainly that you will have only two outcomes of any match (a win or a loss) vs. a set of outcomes (depending on games won/lost difference) and therefore there will be way less data for algorithm to crunch. Not that such a system is unheard of - Rogers tennis ranking in Canada is based purely on win/loss (and the 'weight' of the match, some matches are treated more importantly than others). FIFA ranking (which is actually very similar) uses a hybrid method - it cares about both pure win/loss, but also takes into account goal differential (which is equivalent to games differential in tennis).

All of those WTF-like cited cases are likely outliers anyway. The system overall is pretty accurate and serves the purpose. plus it is easy to say 'flawed system' - why don't you propose a better one? I'm sure it will have many edge cases where it will seem illogical (to an untrained eye of course).

I don't think NTRP is entirely based on ELO since ELO only considers win/loss/tie and doesn't use any type of game differential like number of moves whereas NTRP is just the opposite. I don't think most people here who have issues with the NTRP are arguing that it should not incorporate score and dynamic rating differentials into the formula but that it should also incorporate win/loss into it. Hybrid systems which use both exist so it is not beyond the realm of possibility to think that the USTA could also include it.

LuckyR 11-30-2012 12:36 PM

Quote:

Originally Posted by jmnk (Post 7039977)
not sure what sandbagging has to do with this discussion. Are you suggesting that one cannot sandbag by outright losing the match rather than winning it closely? Could you kindly clarify what your point is?

I'm not sure why you think that 3.89 DR is 'slightly above' halfway ranking? Halfway is 3.75. 3.89 is way more that slightly above halfway. Also, next time you make an assumption that is not obvious to anyone but you yourself, please make it clear. Rather than, you know, implying that someone else does not know what 0.5^15 is.
But if you want to discuss a case where someone is indeed at the halfway point, at 3.75. in this case he needs to get his ranking up by .25 points to get bumped. It is significantly harder to earn this .25 dynamic ranking points. Someone who started at 3.89 needs only .11 to get bumped. It really all evens out - you start at the higher DR, you need to play better opponents to move your DR up, but you only need to move up by a small amount. You start at lower DR - it is easier to earn DR points (because you are more likely to meet higher ranked opponents more often) but you need to earn more of those DR points. the system actually makes it all take into consideration which makes it, I don't know, logical?

could you elaborate on what you mean? the expected score takes into consideration dynamic rating, not your NTPR one.
There's no system in the world that would prevent sandbagging. None. Except having all players play in one single category. Do you really want that?

really. you are sure of that. how exactly? do you have some stats? data? dizzlmcwizzl gave you a perfect example of why going by W/L is no better.

If you go by W/L, and a player wants to get bumped - he just needs to play at #3 (assuming this is a 3 players team, singles only). He is likely to play weaker opponents. You are essentially saying that a player beating 3.60 DR players 10 times is vastly better (and should get moved up) than a player who plays 3.80 DR players and has 4/6 W/L ratio. really? that is logical?

(i do think that not separating doubles and singles as far as rating is concerned is the biggest flaw of the system).

Wow, to quote Cool Hand Luke "what we've got here is failure to communicate". I apologize for for being extremely difficult to understand.

A couple of background things:

1- I don't personally believe that how well any player plays the game of tennis can be quantified to three significant digits. Sure the ratings exist, but IMO the science of using rating numbers to predict outcome of matchplay is too poor to justify that level of implied confidence. In my experience the standard deviation of quality of play is so wide that 2 significant digits is suspect, if you don't believe me, ask Lukas Rosol...

2- Regardless of the numerical system, there are players whose numerical rating does not correlate to their quality of play, on purpose, that is they give false information to manipulate the rating. That difference I call Sandbagging and can result in playing matches against better competition who have lower ratings. I was trying, unsuccessfully, to explain that nuance in my last post, first paragraph.

3- I agree that no system will "prevent" sandbagging. As long as people are willing to throw matches completely that will be possible. But this system creates sandbaggers. Using your scenario, the player who is 3.99, will likely always play someone lower rated than they are and thus will go 15-0, as you cite. The system is completely unequipped to deal with the 3.99 who improves their quality of play, yet never "plays up" to 4.5 (as a 4.0). Never gets to demonstrate their improvement against better competition and never gets moved up.

4- You are right that a straight W/L system will incorrectly bump people up who just randomly happened to play a bunch of players at the low end of the scale, you noted that a 3.89 (in the absence of sandbagging) would do so about 2% of the time in a 15 match season. OK you got me, you keep that guy at 4.0, I move him up (incorrectly BTW 2% of the time, your number) to 4.5 Well that 2% of the time in my system what happens? He gets killed playing 4.25s as a 3.89. Next season, he's a 4.0 Self correcting system. At least as a consolation, in a W/L system, no one wonders "why am I playing the 15-0 guy from last year?"

5- The unaddressed issue is the opposite scenario: what about the 4.11 (playing 4.5) who goes 0-15 for the exact same reason the 3.89 goes 15-0? Does that guy get a break? Nope.

6- How better to acknowledge that you do in fact know what a simple mathematical computation is more clearly than by stating: "As you know..."?

7- When you beat someone or get beat 6-0, 6-0 do you think: "I think we were probably mismatched" or "logical score between correctly rated players"? Of course both are possible (what the USTA says), but in your opinion which is more likely?

Ultimately it boils down to this: what is more likely to happen and what is more likely to kill the fun factor of league play: A) a system that thinks it can predict outcomes by rating and only moves players relatively if they behave unexpectedly and beat a "better" player, regardless of how many "lesser" players they smear the court with or B) a system that acknowledges that matchplay is unpredictable for numerous reasons (I agree cheating is one, but a rare one) and figures that the quality of opponents will even out in the end, so a 15-0 guy is likely better than his competition and moves him up?

Either is reasonable but I feel, obviously, that B is less likely to mislabel players, especially in the long haul, as it is self correcting


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