WellSpyder Posted March 12, 2012 Report Share Posted March 12, 2012 We have a Cross-IMP pairs at the Young Chelsea every Friday night, and those events all have grading information alongside them. The only event that caused a problem was the Swiss Pairs with IMP scoring, which has already been noted and was apparently the only one of its kind so far submitted (though we are having another on April 1st).Thanks, Gordon. That does rather tend to reinforce my suspicion that for some reason the Oxfordshire Bridge Association events on the first Tuesday of every month have been omitted from the analysis. Unlike yours, these are Butlered rather than cross-imped ( :( ), but the system documentation is clear about how these should be handled, too (and no, it's not the same, since as we discussed not long ago on a different thread, these two forms of scoring don't do the same thing - in particular they have different variances). Quote Link to comment Share on other sites More sharing options...
MickyB Posted March 12, 2012 Report Share Posted March 12, 2012 I notice from the indivudual session records for what I have played in recently that none of the imp-ed pairs events have any grading information alongside them There are lots of pairs sessions that don't have grading info alongside in my records, no idea why, but I wouldn't assume the IMP pairs haven't been graded just because the numbers aren't there. Quote Link to comment Share on other sites More sharing options...
mr1303 Posted March 12, 2012 Report Share Posted March 12, 2012 I can see that this is an improvement on "Master Points" Completely 100% agree with this. But if you've been collecting them for years, how do you feel about their devaluation? Quote Link to comment Share on other sites More sharing options...
Vampyr Posted March 12, 2012 Report Share Posted March 12, 2012 5) NGS does use IMP scored pairs events not just MP. How do you convert the IMPs to percentages? At the YC sometimes +95 is the winning score, sometimes +30. How are these and scores in the middle treated differently/the same? Quote Link to comment Share on other sites More sharing options...
gnasher Posted March 12, 2012 Report Share Posted March 12, 2012 How do you convert the IMPs to percentages? At the YC sometimes +95 is the winning score, sometimes +30. How are these and scores in the middle treated differently/the same? Haven't you read the NGS Guide? Search for "Butler Pairs" and "cross-imped pairs". At Cross-IMPs, a score of +30 over 24 boards is treated as equivalent to about 58%; +90 is worth about 74%. That seems reasonable to me. Quote Link to comment Share on other sites More sharing options...
gordontd Posted March 12, 2012 Report Share Posted March 12, 2012 At Cross-IMPs, a score of +30 over 24 boards is treated as equivalent to about 58%; +90 is worth about 74%. That seems reasonable to me.That's a little more generous than the YC tables that are used for converting for Ladder purposes. They would give a little over 57% for +30 & a bit over 71% for +90. Quote Link to comment Share on other sites More sharing options...
Vampyr Posted March 12, 2012 Report Share Posted March 12, 2012 At Cross-IMPs, a score of +30 over 24 boards is treated as equivalent to about 58%; +90 is worth about 74%. That seems reasonable to me. Perhaps. I just feel that there is a difference between scoring +30 IMPs and winning and scoring +30 IMPs and coming in 8th. Maybe they should be treated as the same (excluding prize money!)? Also in the document it says nothing about taking into account the size of the field. Shouldn't this matter? Quote Link to comment Share on other sites More sharing options...
gordontd Posted March 12, 2012 Report Share Posted March 12, 2012 I just feel that there is a difference between scoring +30 IMPs and winning and scoring +30 IMPs and winning. I confess the difference escapes me. Quote Link to comment Share on other sites More sharing options...
Vampyr Posted March 12, 2012 Report Share Posted March 12, 2012 I confess the difference escapes me. LOL Post corrected. Quote Link to comment Share on other sites More sharing options...
Finch Posted March 12, 2012 Report Share Posted March 12, 2012 Perhaps. I just feel that there is a difference between scoring +30 IMPs and winning and scoring +30 IMPs and coming in 8th. Maybe they should be treated as the same (excluding prize money!)? Also in the document it says nothing about taking into account the size of the field. Shouldn't this matter? You mean, just like the difference between scoring 60% at matchpointed pairs and winning and scoring 60% and coming in 8th? The difference still escapes me. 1 Quote Link to comment Share on other sites More sharing options...
Vampyr Posted March 13, 2012 Report Share Posted March 13, 2012 You mean, just like the difference between scoring 60% at matchpointed pairs and winning and scoring 60% and coming in 8th? The difference still escapes me. I think that the size of the field and the variance of the scores are relevant in both IMPs and MPs. Quote Link to comment Share on other sites More sharing options...
awm Posted March 13, 2012 Report Share Posted March 13, 2012 I think that the size of the field and the variance of the scores are relevant in both IMPs and MPs. Well the size of the field certainly effects your chances of winning, but I'm not sure it has much effect on your expected percentage. I mean, if I expect to score 55% on average in a small game, I'd expect to score the same in a larger game of the same average caliber right? Maybe variance goes down. The variance might be an issue in the short term, but again if you're trying to measure my "average score" it should even out over enough sessions (which obviously takes a while). Quote Link to comment Share on other sites More sharing options...
phil_20686 Posted March 13, 2012 Author Report Share Posted March 13, 2012 Well the size of the field certainly effects your chances of winning, but I'm not sure it has much effect on your expected percentage. I mean, if I expect to score 55% on average in a small game, I'd expect to score the same in a larger game of the same average caliber right? Maybe variance goes down. The variance might be an issue in the short term, but again if you're trying to measure my "average score" it should even out over enough sessions (which obviously takes a while). I think the point Stefanie was trying to make, is that the variance on a set of hands scored for MP is probably not as large as the variance of a bunch of IMP hands. E.g. If I deal two sets of boards, the first set all partscores, and the second set all games and slams. Then I might be able to rack in a huge "equivalent MP" score on the second, while being unable to on the first, while I would have the same score had I scored them at MP. There are lots of things you could in theory do for this, like scale the imp scores onto the average normal distribution for a MP score, but it would probably be a lot of effort for a minimal game, since there are not all that many imp pairs sessions anyway. Quote Link to comment Share on other sites More sharing options...
mchristie Posted March 13, 2012 Report Share Posted March 13, 2012 Just to say that, due to a display quirk, (well, ok, a bug) it is somewhat random whether you will see your NGS result for any multi-section pairs event, but it will have been scored, and if so it will affect your grade. Hopefully the display will be corrected later this month.Various IMP scored results, especially in Oxfordshire, have not been graded due to a bug in the reporting of these results by the scoring system.IMP results are compared to MP results and the conversion factor is essentially the ratio of the observed variances of IMP and MP scores for fields of equal players. (That doesn't read very clearly, sorry.) I'd like to use our large database of both MP and IMP events to refine these observations. Some day, year... Quote Link to comment Share on other sites More sharing options...
Vampyr Posted March 14, 2012 Report Share Posted March 14, 2012 I think the point Stefanie was trying to make, is that the variance on a set of hands scored for MP is probably not as large as the variance of a bunch of IMP hands. Yes; I wish I had expressed it half as well as in this post.it would probably be a lot of effort for a minimal game, since there are not all that many imp pairs sessions anyway. But for a lot of people IMP pairs represents a large majority of the club bridge, or (EBU affiliated) bridge period, that they play. Even though it is only once a week. Also, there seems to be a lot of "this effect is small, so we will ignore it" and "we can't do anything about that effect, but it only affects about 10% of the people" etc. This all adds up. Quote Link to comment Share on other sites More sharing options...
Blue Uriah Posted March 14, 2012 Report Share Posted March 14, 2012 Yes; I wish I had expressed it half as well as in this post. But for a lot of people IMP pairs represents a large majority of the club bridge, or (EBU affiliated) bridge period, that they play. Even though it is only once a week. Also, there seems to be a lot of "this effect is small, so we will ignore it" and "we can't do anything about that effect, but it only affects about 10% of the people" etc. This all adds up.Since Christmas there have been over 10,000 club sessions submitted to the EBU and 0.7% of those have been Butler Pairs, 0.5% Cross-IMPs. So I'd be very surprised if there were many people for whom this represented a "large majority". Still, to suggest that the EBU doesn't care about this tiny group is a little unfair. The conversion tables have been put together by some very clever people over years of study and trial and, personally, I'm at least willing to give it a chance before dismissing it so readily. Quote Link to comment Share on other sites More sharing options...
mchristie Posted March 14, 2012 Report Share Posted March 14, 2012 At both MPs and IMPs some boards are more variable (wilder) than others which are flatter, and there is less opportunity to score well/badly on the flatter boards. We know that there are comparatively few extremely significant boards at IMPs whereas at MPs it is the extremely flat boards that are less common. What we compare when converting IMP scores to MP% equivalents is the average variability of IMP boards and the average variability of MP boards, based on actual data from a large set of boards, so that we CAN say the average variability of a bunch of MP boards is equal to the average variability of a bunch of IMP boards.Stephanie, I think this means we treat IMP pairs events fairly. It certainly isn't meant to be in the group of small effects that we ignore. Quote Link to comment Share on other sites More sharing options...
ahydra Posted March 14, 2012 Report Share Posted March 14, 2012 Wow I'm a King! (59%) Doubt it'll last though. ahydra Quote Link to comment Share on other sites More sharing options...
billw55 Posted March 14, 2012 Report Share Posted March 14, 2012 I think it would be an interesting experiment to send a large number of predealt boards to matchpoint games in one region, and IMP pair games in another, and then analyze the results. Quote Link to comment Share on other sites More sharing options...
IanPayn Posted March 14, 2012 Report Share Posted March 14, 2012 You mean, just like the difference between scoring 60% at matchpointed pairs and winning and scoring 60% and coming in 8th? The difference still escapes me. ++++In the first instance you feel fate has smiled upon you. In the second instance you feel hard-done by. It all comes back to feelings. Quote Link to comment Share on other sites More sharing options...
JLOGIC Posted March 14, 2012 Report Share Posted March 14, 2012 Gnasher up to 63 makes the ratings seem way more legit somehow :P lol bbfanboism. Anyways, I think this is a great idea, I hope it works and USA implements it. Ratings make people play more, not less. Quote Link to comment Share on other sites More sharing options...
billw55 Posted March 14, 2012 Report Share Posted March 14, 2012 Anyways, I think this is a great idea, I hope it works and USA implements it. Ratings make people play more, not less.I wonder. I think most likely you are right. But I also think that there will be a nontrivial minority who begin engaging in rating protection - various metatactics designed to maintain an otherwise unsustainably high rating. In some cases this would probably include playing less, as well as careful selection of opponents, partners, events, etc. The upside of nondecreasing masterpoints is that there is never anything to lose by playing. 1 Quote Link to comment Share on other sites More sharing options...
gnasher Posted March 15, 2012 Report Share Posted March 15, 2012 A friend of mine has just asked me for a game. In round numbers, I am rated 63 and he is 70. The average field at the Young Chelsea is about 55. Does that mean we have to score 61.5% (or +43 IMPs) just to break even? Help! Quote Link to comment Share on other sites More sharing options...
WellSpyder Posted March 15, 2012 Report Share Posted March 15, 2012 A friend of mine has just asked me for a game. In round numbers, I am rated 63 and he is 70. The average field at the Young Chealsea is about 55. Does that mean we have to score 61.5% (or +43 IMPs) just to break even? Help!Yes, it does. Does that mean you won't agree to play? I doubt it! In any case, once the grades have settled down you will probably find that around half your sessions fail to break even in the sense you have used it above. Quote Link to comment Share on other sites More sharing options...
gnasher Posted March 15, 2012 Report Share Posted March 15, 2012 We decided that the best thing to do was to play on Friday 13th. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.