tnevolin

Hi, kwiktrix. Sorry for late reply. I kind of abandoned this thread for a while. 1) Combined, of course! It is a partnership who takes trick in bridge, not the individual player. 2) Yes, they are. 3) Absolutely. That is the core of my analysis and calculation. In fact, it is not even a comparison. I directly adjust coefficients to match the reality better. I don't use DD or SD emulation, though. The only thing I do is comparing my results to actual tricks taken in the game (average across the table, that's it). I am not sure how to describe degree of fit because the approach is complex by task nature and my program is not 100% academic. I do some tests those seem to be enough to convince me in good match but nothing fancy like Xi-square, etc. Correlation does not go through (0,0). 4) Sure. See below. Here is the folder with all related documentation https://drive.google.com/drive/u/0/folders/0BxM2JfK2YtucYmhjdThEOHhXTU0 Specifically, Calculation rules https://drive.google.com/open?id=0BxM2JfK2YtucRzVOTjZJcXlfa0k Method history and description (plus some relevant information) https://drive.google.com/open?id=0BxM2JfK2YtucWW10bndERmd2NzQ

Hi Everybody. Sorry that I disappeared for a while. I was regrouping my calculation to optimize score improvement as well as trick prediction. Essensially I am trying to maximize the potential score (MPP and IMP) that my evaluation system would give to players. It is not finalized yet and I stumbled accross one formalization problem and I hope you can help me. I am formalizing hand features for NT contract. Most of them are simple like high cards, long suit, high cards in long suit (the source of extra tricks). However, there is another important features affecting NT games outcome: stoppers. Usually it is the weakest and shortest suit that is the most dangerous for NT contract. Unfortunately, there are many factors and it is not easy to mathematically determine which suit is most beneficial for defenders. For example, you have short suit with very strong cards (AK) or long suit with very weak cards (T9876) - which one is to select as worst stopper? Another problem that stopper is a combined partnership effort. Partners surely can exchange each one best stoppers but it still unclear how to predict which suit will be defenders attack target because mere flag "stopper or no stopper" doesn't disclose information about partner's suit strength. What if partner showed stopper and you have another 3 low cards in it - does it make it significatly stronger? With partner's Kxx it doesn't, but with partner's Jxxx it gives only 6 cards to defenders lowering the risk of attack. And many more. I would appreciate any suggestion on the topic. Try to think in formal terms (card face values, suit length, plus vague information about partner's declared stoppers) so that others can apply your rule without ambiguity. Thank you.

Good suggestions. I accualy tried something similar just more generic. Very roughly estimated number of tricks: for NT = HCP/3 + 1, for suit = HCP/3 + combined trumps/2 + 1. Then if result differs from estimated by 6 tricks I throw whole section away assuming that the same person entering the data could make other mistakes. You can look at examples here: http://www.bridgebase.com/vugraph_archives/vugraph_archives.php. Most common errors are typos, missing results, missing hands, impossible hands (duplicate cards, missing cards). The only one non typo error I found is swapped N-S, E-W hands. So the contract says something like 4HE but it was S who played it. Grrrr. I don't remember the exact vugraph but it is one on their page. You can even see the movie for it with this error right in plain sight.

One good news and one bad news. I found a large game archive on BBO vugraph page. It is quite extensive: 400+k boards. Unfortunately, they all are manually entered and there are a lot of typos and mistakes. Some of them are easy detectable like impossible deal. Some of the are very hard to detect like one vugraph I found had N-S and E-W hands swapped. A very nasty error. When such error enter into analysis they pollute results. I am trying to devise empiric rules to filter such mistakes out. Anybody can propose such rule? I would prefer to filter out extra to make sure that rest of the observations are clean rather than leave incorrect entries. Thank you.

Parsed both pages for 2k records. Not too much. Some text on the second page says there are a lot of free PBN data in Gib or some other sites but I never found them in open access. Anybody uses Gib? Is there a free PBN database there?

I scanned all the events, rounds, tables and Boards there are. Apparently they just started recording boards since 11. That's all they have.

I finally downloaded them! Thanks for interesting source. The sad thing is that there is only 10k boards there. A tiny amount. :( Anybody knows some similar sources?

I like the link and the study. I even send the man a message but he didn't reply yet. Do you know him personally?

I know this research. This is specially true for NT contracts. It could be explained by lack of entries to weak hand and, therefore, lack of maneuver. I tried to factor it into the calculation. Didn't work well for two reasons. First, the effect is very subtle and there are not much hands with large skew like 24-0. Probably need larger dataset to catch it. Second, and more important one, is that this is second iteration factor. I.e. you need to evaluate your hands first and then do a second iteration for this adjustment. I decided not to include them for now as it complicates evaluation rules tremendously.

Yep, the idea exactly. Help people to make most difficult and important decision there in the game.

You results and conclusion correspond to my findings exactly. My 3NT contract requirements are 25 for IMP and 26 for MP. I just often replace 25/26 with 25 for the sake or simplicity. Then if we shift it 2 points down, as I explained in my initial post, we would get the results for Evolin points without constant which almost exactly corresponds to HCP. And here you get your 23(IMP)/24(MP) borderlines! If you use pure score and calculate what probability you need to win 3NT to still profit on average, you would get 40% (nv), 33% (v). Jamming v and nv together it'll be somewhere 37%. Of course, game points is not equivalent to IMP but they are good approximation.

You lost me. Isn't it what we started with?

I know some. The problem here is that there is a correlation between number of tricks and contract level. So if someone bid 3NT that means they have around 9 tricks. Maybe some more or less but not the whole lot. So if I restrict whole set to only those bidding 3NT I will get a conditional result that in simple human words would read: "If we bid 3NT and have so much points - how many tricks we have?". When you rephase it like this it is obvious that you don't even need statistical analysis to know that the answer will be somewhere in 8.5 - 9.5. I actually did what you proposed. Tried to narrow down to the interval of interest. Like if I would want to predict 3NT games better and don't care about 1NT, I would just cut out interval where people bid (or get) 8-10 tricks. Sounds promising but it didn't work. The coefficient values becomes ridiculous. Like I would get one huge constant of 9 tricks plus some very small coefficients for other features to account for slight variation around 9 tricks. And the overall prediction around 3NT got worse comparing with the case where I considered whole range of games.

You are right, jogs. This is a inherent skew that all analysts are pointing out. Number of tricks depends on contract because both declarer and defenders tacktics is driven by it. Unfotunately, I don't know a cure. I also didn't see anybody posting a good idea how to filter this skeweness out in analysis.

Nice link. Let me study it. Maybe I indeed have some statistical error inside.