nigel_k

It depends on what assumptions you make about what will happen at the other table(s). For small slams at IMPS, assuming they bid either game or small slam in the same denomination at the other table, you need 50%. This is because you stand to gain 11 imps non vul or 13 imps vul and lose the same number. For example if you are -100 and they are +650 you lose 13, while if you are +1430 and they are +680 you gain 13. For grand slams at IMPs, assuming they play in either small slam or grand slam, you need about 56%. Non vul you gain 11 or lose 14 so need 14/25. Vul you gain 17 or lose 13 so need 17/30. Obviously the assumption about the other table is more likely to hold in the small slam case than the grand slam case. You don't want to go one down in 7 when opponents play in game. If the assumptions are unreliable you need a better chance of success. Some of the things mentioned below about matchpoints also apply at IMPs, especially if opponents are not strong. At pairs there are more factors to consider. Any time there is a possibility of others playing in the wrong strain you want to be conservative. If the opponent do any bidding or you used any sort of convention such as fourth suit forcing then usually some tables will find a way to screw up and you can beat them just by making game. If there is a chance of gaining a trick in the play you also want to be conservative. With a 5-3 major fit and significant extra values often 3NT and 4 of a major make the same number of tricks. If the slam is 50% and half the field bids it you can play 3NT and get half the matchpoints when the slam makes (because you beat everyone in 4 of a major) and all the matchpoints when the slam fails. If it's a minor suit slam, plenty of tables will play 3NT and you need to consider how that will go. If 3NT is likely to make an overtrick there's not much point in stopping in 5 of a minor. If 3NT is unlikely to make an overtrick there's no need to bid slam. If there are no such special considerations, a slam needing a finesse at worst is ok at matchpoints. You certainly should be much more conservative with grand slams at MPs compared to IMPs though it's hard to put a figure on it. To some extent the percentage required is academic because the likelihood of making will seldom fall between 68% and 90%. You want to bid the 90% ones and the occasional 84% ones. The main problem hands are where you need a 3-2 break, i.e. 68%. As above, if your fit is 5-3, 6NT may make the same number and you can get most of the matchpoints without risk by doing that. If the fit is 4-4 in a minor you need to consider whether 6NT may make 6 when the minor makes 7. You want to bid 7 if it does and stop in 6 if it doesn't. If the fit is 4-4 in a major and you expect the field to find that fit, then you probably should bid a 68% grand. There is always a chance partner will turn up with the jack or ten and you are much better than 68%. Hope this helps. Nigel.

The ability to analyze a hand is itself a skill you need to master. You need it when playing and also when evaluating your performance. I don't know what level you are at exactly, but many people never progress beyond noticing that a different bid or play would have worked and concluding they made a mistake. You need to go further and identify the layouts where your choice succeeds and fails and estimate the relative likelihood of both based on the evidence from the bidding and play. This is an essential preliminary step to becoming a good player. Second, I highly recommend learning from watching experts. Get hand records from top level events (there are various ways to do this) and bid and play the hands yourself, covering the 'unseen' hands if you find that helps. Then compare with what the experts did. If you can't figure out why they did something, post the hand here. Third, don't worry too much about results. If you are constantly studying and learning, results will come.

What Ken said. Opposite a help suit game try, partner will value secondary honours or a shortage because those will cover your losers. So 2S is better than 3D because he won't have secondary diamond honours and a diamond shortage isn't that good for you. It also saves space which is a bonus. On the actual hand, partner should probably have bid 4H or 3NT. He's maximum and his cards are not terrible even opposite a diamond try. You should maybe have bid 4H directly, especially if partner would respond 1NT with a bad heart raise. Also, you might consider 2NT as a game try (not necessarily balanced) when no other try fits. On the actual hand your spades might be ok even opposite three small. If they were better (eg AJT) a help suit try in spades wouldn't really do much for you.

Simulating two balanced hands of approximately equal strength and no 8 card major fit, I get: Combined 24 HCP: less than 8 tricks 24.40%, 8 tricks 39.58%, more than 8 tricks 36.02% Combined 25 HCP: less than 8 tricks 12.41%, 8 tricks 31.94%, more than 8 tricks 55.65% Bidding 3NT with 24 combined HCP therefore has a gain of 0.5 IMPs per board when vul. To avoid underbidding you have to take into account the times you only lose 3 IMPs because 2NT doesn't make. Non-vul you lose 0.3 IMPs per board bidding game with 24 HCP but gain 1.5 when holding 25 HCP. So this suggests bidding game any time you have a better than average 24. Plus, they always find the right lead double dummy but not in real life, especially after 1NT-3NT. So a good rule of thumb is probably that 24 HCP is enough for 3NT. Regarding the 4333 shape, I wouldn't adjust it at all for NT bidding. For example I simulated KJ92 A32 32 KQ32 and KJ92 A32 432 KQ2 opposite a balanced 11 and they came out almost identical. Certainly an extra nine (maybe even an eight) would more than compensate for the difference between 4333 and 4432. Obviously it's different at pairs because you want a higher chance of making and would like to stay with the field (to the extent you can when playing a 13-15 NT).

Obviously if you were aware there would be a third round then this is a great plan, but with no assurance that the opps will help you out and bid 3C I think you are resulting to suggest 2S on the second round. Partner will not think twice before passing with x Jxxxx Jxx xxxx or similar. Obviously 2S on the second round doesn't work on the example hand above, but does on other hands such as Qxx Jxx Jxx xxxx. It's a question of choosing the percentage action and can't be resolved by quoting a single hand. My view (admittedly just a gut feeling) I think it's best to bid spades on either the first or second round. Two (or three) takeout doubles without bidding a decent five card major leads to the wrong strain more often than a suit followed by double. If the hand was a bit weaker, I would definitely overcall 1S. The actual hand is close between 1S and double.