coyot

Quick comment: This analysis would appear to ignore conditional probabilities... The odds that partner holds 11-12 HCP changes based on the strength in your hand. The easiest way to solve the original problem is to make use of some form of Monte Carlo simulation using a program like Dealer... Ideally, you would want to calculate the odds that Responder holds 11-12 HCP and no 4 card major given that 1. Dealer has a 1m opening and 2. RHO does not have a hand suitable for an overcall If you read the bit you quoted correctly, you will find that I mentioned that the probability is lower :-). Since the resulting probabilities are between 0.5% and 1% anyway, it does not make a big difference if the chance drops by i.e. 20%... From what it seemed to me, ArcLight was interested in finding out whether these hands do in real play appear often enough to worry about losing 2NT natural bid... Opponent's overcall lowers the chance of 1x-2NT natural bids even more, too... so the real life odds that you'd have a 2NT natural response (with no other bid) are somewhere about 0.3-0.4% after minors and hearts and about 0.9% against spade opener... which is sufficiently low to scrap the bid

No idea about a search engine that could tell this... But, my experience is: Against opening 1♣, you never need 2NT, because even with 3-3-4-3 you can bid 1d and then 2NT any likely response (with no long suits, you still need p. to find extra values with weak NT hand (or with long club hand). Against 1♦, you only have problems with 3-3-3-4 - and the easiest approach would be to treat bad 11 as 10 and good 11 as 12 :-) - or even have the 1NT response defined as 6-11. (With totally misfit hands, you'll hardly make 3NT on 25 HCP - and p with 5 clubs and good 14(15) HCP will raise (as he is known not to have 15-17 balanced or 16+ with 5-4... Googling for "bridge card distribution probabilities" provides helpful link: http://www.xs4all.nl/~tpgroen/bridge/index.shtml 4-3-3-3 with 4 cards in a specific suits has a chance of 2.6%. Point count 11 or 12 sums about 16%, so against an opening of 1m, the odds of getting a hand that could only be bid as 2NT are about 0.4% (maybe a little less, because the 11-12 point count is general probability, not affected by the fact that partner has already opened bidding (which gives the remaning 3x13 cards less total points than the 10 average). So, against minor openers, the 2NT 11-12 occurs very rarely - less than 0.5%. (The only question is, how often will you bid 2NT when you COULD bid differently, to hide your major holdings :ph34r:) Against major openers, the artifical 2NT is a must. In 2/1 system, you're in the clear with 1NT semiforcing as declarer will pass only with a very bare minimum (if ever allowed by the system) - so with any 11 (and even bad 12) you can afford 1NT, while with good 12 a 2/1 bid on minor 4card saves the day. The frequency of these cases is much higher, though, because it covers every distribution with a doubleton in partner's suit, where the three remaining suits are divided 533 or 443 (for 11 HCP) or 433 (for 12 HCP). For 1H opener, the probability is lowered by the chance of responder having 4card in spades. So, roughly: (0.15 + 0.21) * 0.25 (specific doubleton) * 0.08% (11HCP) =~ 0.7% (0.21)*0.25*0.08 (12HCP) = ~ 0.3%. Against opening 1♠, there is approximately 1% (max. 1.2% wild guess) chance that you have a natural 2NT raise. Against 1♥, the chance would be lowered to about 0.5% or less. (1/3 of 5332 and 2/3 of 4432 11HCP hands scratched, 2/3 of 4432 12HCP hands scratched.)

I mentioned above that there are two topics hidden in this: 1) How to keep the abuse at reasonable level (TD work, punishing bidders... is everyone going to call director when opponents give him 24 IMPs?) 2) Is the current scoring system fair? While topic 1) has been settled (call TDs, report freak bidders to abuse@... and blacklist them if you're TD), topic 2) is quite interesting alone. I personally find Butler with it's extreme cuts more fair in general than CrossIMPs. CrossIMPs are about the only feature of BBO that I dislike - because without the cuts, you're bound to get undeserved points (either way)... Once I observed to a friend when explaining online bridge that for every 8-trick contract there will be one or two pairs playing game and for every game contract there will be one or two pairs playing a slam... P.S. Working link to Bastille: http://users.skynet.be/hermandw/bridge/calcula/calcul16.html

I would imagine my partner holding something like AKx-Axxxxxxx-void-Kx. The diamond void effectively denies him RKCB - any my bidding denies him the club cuebid. Based on bidding and my hand only: Anyway, I'd pass 5♥ without much thinking because the only sensible explanation of this bid would be "partner, I need some trump honors and have no way of asking about them." If he wants to play in diamonds (and cannot use RKCB with a small club doubleton), he can bid 5♦ instead of 5♥ - I will figure out that he has 3-5-3-2 and hopes to find a club stopper in my hand. Seeing the actual hand of responder, I would prefer 5♣ bid after 4♥. I would expect partner to realize that since I am pushing to slam against two diamond bids, I have some use for diamond values - and I have shown stoppers in both black suits... He then sees working diamonds and heart queen and will hopefully bid 6.

If you play Walsh XYNT, 1♥ denies balanced hand. I am used to play ♠ as universal: Opener with spade 4card will raise and I will either bid 3NT or 4♠ depending on what I have. Opener without spade 4card will bid 1NT with 3card and stopper or doubleton with two stoppers, otherwise he bids clubs again. 1♣-1♦-1♥-2♠ would therefore be splinter :-) (showing 1453 distribution and GF values). With a pickup partner on BBO, I would most likely treat jump to 2♠ as FSF and show stopper or halfstopper (3♠) (as splinters without agreement are usually costly :ph34r:) and would treat 1♠ as possibly natural (same bidding as above).

Oh, I see... you would have to use continuous IMP scale to get rid of this problem... that 910 Butler average happens to be near to the wrong (for NS) boundary on IMP scale... To the quoted part: If 12 of 13 pairs risked the game, I don't think they deserve any extra points... When the whole field bids it except for some natural pessimist, they don't play "better" bridge than the rest of the field. It is only the pessimist that should suffer on this board. I think that we can safely assume that if a large majority of the field ends up in a game contract, the game contract should be considered "par of the board" and only those that score more than par should receive points. If you look at it from the defending side: who are we to assume that the 12 NS pairs who bid the game play better bridge than the 12 EW pairs that just lost 0.83 IMP? I think the scoring system should try it's best to reward those who play better bridge... Who are we to assume that it is a universal flat board because only 1 out of 13 pairs misses the game. Pardon me, but I thought that the definition of "flat board" IS a board where a large majority of pairs playing common bidding systems and not affected by opponents psycho bids end up in the same contract and score the same result. Even if there are alternative ways of making the contract, if the large majority of pairs choses the one that succeeds, I consider it a flat board. but who knows, maybe this is a board that only 12 out of 13 pairs will risk game on It's about the same risk as betting that the next US president will be either a Democrat or a Republican... 12 of 13 people think so... and that is why no betting agency ever runs bets like this with win:bet ratio above 1 :ph34r:). In other words - cutting the extreme results would bring more good than bad - and it would bring the good largely to the pairs that were not able to affect the result significantly. There is the question if and how could extreme-cutting be incorporated into cross-imps - how to determine the score for the pairs whose results were cut out as extreme (in order not to disrupt the IMP balance etc...) IMHO Butler with fractional IMP scale would work quite well. We're using normalized IMPs with decimal parts already (although they have their nice whole IMPs behind them) and I think it would work quite well. [but I promise to stop spamming the forums with this topic if noone else supports the idea :-)]

Oh, I see the difference now... was too lazy to do the experiment and thought that Cross IMPS would produce nearly the same results... I agree with the statement that removing extremes does not purify the average completely in most cases - but you should also consider the effect of Butler-type cuts on flatter hands: When everyone plays 4S= and one pair plays 2S+2, every defending pair will get a bad result "for just sitting there". I'm not sure how seating algorithms work in various BBO tourneys - are they all random enough so that noone will suffer average 1IMP per board for sitting on the same side of the table as some aggresive freaks? (3/4 Howell or Mitchell comes to mind) I personally think that it would be possible to do CrossImps with the Butlerish cut - because the 2.7 IMP difference between CrossIMPs and Butler in the example is caused by the fact that two pairs went down one in the slam. This causes the difference between CrossIMP 3.29 and Butler 6IMP penalty for not reaching the small slam. Butler has the advantage that it's cuts protect the innocent from one freaky pair - and while it's critics may rightfully claim that you get scored against a non-makable score, I would only say that in the long term, it does not really matter. If half of the field bids the slam and half does not, your average IMP gain in CrossIMP will STILL look like a comparison to non-makeable score. I don't understand the part that says that Butler compares to -18... how does the number of results come into it?

1) Results for the extremes are calculated, of course, by comparison to the "cleaned" average. 2) What is the purpose of IMP scoring, compared to matchpoints? That the more extreme result you get, the bigger score you get. But, for example, playing in Main Bridge Club at a table, you would want your scoring to reflect, if possible, the ability of your pair to outbid and outplay the opponents against something that should be called the "par of the board". The score I achieve at the table should be the least possibly affected by one of the other 15 pairs having an honest disaster. 3) You seem to have misunderstood me. In fact, the top scorers will get extra benefit. If there is a laydown 3NT for +600 and 15 pairs end up in the right contract, the ones that score 150 for 2NT+1 will NOT cause the 15 pairs to receive +1 IMP for doing right. (And, which is even more important, they will not cause the other 15 pairs (defending a laydown game) to receive -1IMP for doing nothing wrong. They will be the only suffering pair, suffering the full 450 points penalty... Again: the general principle is that you discard i.e. one extreme result from each end (for 16 results), determine the IMP average and then score all 16 boards against this simple average. This way, one freak result does not change the par of the board - while both pairs involved in that freak result get their big win/loss - possibly even slightly bigger than under current conditions...

Hello! There is one thing I miss in the country filter - and that is presets. The one preset I would be very glad to see is fellow countrymen. Would it be possible to add a button that sets the country filter to match the country of the player? This should be quite easy to implement. More complicated but fairly useful: a) custom preset (perhaps .ini file) :unsure: some prepared presets - the first idea that comes to mind would be language-based At least English/French/Spanish/Portuguese/Russian/German are languages that are spoken each in several countries and so it would be nice to be able to filter players by language. c) this would be a lot of work in future - allow players to specify in their profile which language they speak enough to use for bridge. You could then set filters for events/tables.

This is not true. Cuts are possible even if there is no mean. The only thing you need to do is, when walking the list of existing results, find its max and min and skip those. Using sum of IMPs divided by amount of used results is in fact a nice and fair method, because you can gain fractions, i.e. for playing NT instead of major etc. - but it can still involve cuts of extremes. It would only mean that you could not use a simple loop that goes through all results - you would have to use min() and max() functions on the result set and two ifs in the code. It would probably make the whole code significantly slower - but if performance shows as troubling, it can always be reworked from the simple method with mi(), max() and ifs to some cleverer singlepass function. To simplify matters further, the whole recalculation could be done only once when all the results for the board are present - no need to do the cuts on the fly. Now that would be really fairly simple and quick.

I would perhaps want to split this topic into two: 1) Ignoring extreme results when counting IMP average for a board - which has nothing on general to do with abusive players and should be discussed as a separate thread 2) Protecting the whole tournament from abusers. This topic could be discussed from several views: a) spoiling the average (solved by the above) :unsure: giving the defending pair a good result they do not deserve. If the defenders are supposed to refuse the claim and call the director, would not doing so be considered unfair? Would the defenders who gladly accept 24 IMPs be punished for doing so or not? c) giving the TD more work handling these calls. d) reporting to abuse e) catching the offenders automatically by the system. I personally do not fear that the last step would be too difficult. For a first start, two simple conditions could work together: 1) board results in more than 4(5) under/overtricks than bid 2) board score results in more than 300% of average score for this board. These conditions together should cover most of unbid slams and even sacrifices gone way wrong... (i.e. non-vul down 5 against vulnerable game would be 1100 vs 600, still within 200%) If the system could automatically "call" the director (or perhaps notify him in less demanding way), the TD could then be given the choice of either approving the result or assigning ave+ to defenders and some hefty penalty to offenders (plus automatically reporting them to abuse and adding them to a general blacklist). I don't know yet if the scale of this problem is worth such the fuss, though. Maybe a simple check of the results list would show that there are only a few cases each day... Currently I see the biggest problem in the fact that (especially when this happens in the last round of tourney) some TDs do not (for various reasons) act on it. In my case, the defenders scored 24 IMPS on the very last board and won the tournament by about the same margin. I don't know if it is possible for TDs to adjust results when the tournament has already finished - but in this case, when I (accidentaly) discovered this result and told the TD, he said something like he couldn't adjust... if you feel that this problem is not worth any system changes, I would at least propose to employ a very strict policy against those abusers - that is, account ban on 2nd repeat (if not on 1st :)). V.

Hello, folks! I've recenly seen another case of a pair scoring 24 IMPS for 7NTxx-13 with obvious intent (straight bid and 0 tricks claim) by the other pair. It is impossible to prove intent on the receiving end (and I believe that in most cases there is no intent). Most directors do adjust for these results when found - but especially when this happens in the last round, it escapes detection... I think that there should be some significant punishment for people that spoil other people's game this way... the only problem is that things like that are very hard to achieve automatically. One possibility would be to detect all 0 tricks claims by defense at first trick (as these are next to impossible in a real play) - and repeat offenders banned/deleted. Other idea would involve TDs (and that is why I came to this board): Perhaps it would be useful to have the system automatically notify the TDs about any weird results for each board - and they could blacklist the offenders globally... This would be more subtle solution, catching not only the most obvious cases but any freakish results. I imagine that setting the threshold for suspectible results at 300-500% of average (or anything doubled/redoubled and with more than 5 under/overtricks) should be sufficient. What would you think? Is it okay to just trust TDs to catch all those freaks? Or should there be something in the system to punish them as well?