[TheoKole]

I am wondering how often others use these "rules" as a guideline as to double part score contracts by opponents.

By my own records in match-point and team play, they are correct about 5 times out of 6, providing that you have a misfit with partner and a majority of the points for the deal in question. This corresponds very closely to what I have read should be the average success rate of these doubles. I tend to use them in match-point and team play with the same frequency. For information purposes only I have played in about 30 national tournaments in my country and my average success rate is between 1st and 6th place in open competition, however; I have never played in an international tournament or against international players in tournaments.

I noticed recently in Vugraph that very few part score contracts were doubled for penalties in team play, and the commentators went on and on as to how you NEVER double a part score contract unless you are 100% sure that the contract is going down.

The obvious questions come to mind then,
Does the level of play between national and international tournaments matter that much in doubling?
Are swings so rare that even with the mathematics backing you, you just cannot risk being wrong even once?
Am I completely wrong in doubling part scores in team play without 100% certainty?

I have read in Justin's blog, that sometimes paid professionals will not take a semi risky decision that they cannot explain to their teammates if it goes wrong, due to the risk of being fired. Do part score doubles fall into that category of "decisions" and perhaps is a major reason for the "certainty" criteria of the doubles?

All comments and suggestions are welcome but I would truly like to hear the experiences of players that have played in international competitions or against top flight players.

Thanks, Theo

[Yu18772]

I think it is a matter of calculation:
For example 3MX -1 or =, vs 3M -1 or made.

3M make 3 = -140 = 4 IMP
3M make 2 = 50/100 = 1 / 2 IMP
3MX make 3 = -530 / -730 = 11 / 12 IMP
3MX make 2 = 100/200 = 2 / 4 IMP


If ops non vulnerable you stand to gain 1 IMP from the double and loose 7 - therefore you need your close doubles to work better than 7 out of 8 cases (5 out of 6 is not good enough).....when they are vul you stand to gain 2 IMPs, and loose 8, so you need them to work in more than 75% of the cases. In top level knock out teams (which I dont have experience playing), the matches are usually pretty close, so with the added risk of loosing a swing, these odds pretty much translate into "being absolutely sure that they go down". In real life your evaluation of opponents capabilities plays a large role.

[Mbodell]

I don't see why it wouldn't work, although not sure how much it comes in to play that you know you don't have a fit with partner (which also means you are relatively confident that they don't have a great fit either). I hadn't heard of the rule of 10 or the rule of 12 so I had to look them up. I had for a while a similar rule that was based on when partner opened 1nt and I was considering doubling their overcall. Similar to the rules above it is based on us having the balance of the points, and me being able to tell what the maximum fit the opponents have.

It looks like it's a little complicated of a formula, but it is intuitive to work out, even if it isn't to write out. Basically it is our partnership's points and our partnership's cards in their suit adjusted for is it IMP/MP and are they at a higher level or not.

Double if, and only if:

Responder's HCP + min opener's 1nt HCP + Responder's cards in suit + 2 [for worst case opener's cards in suit] > 26 + (imps ? 2 : 0) - (3 * (level - 2)). I tried >= and it mostly works, but I had a few too many makes, so against good players I dropped the =. Against bad players >= is fine.

You hold AJx Qxx Kxxxx Jx and partner opens a 12-14 1nt. Your RHO bids 2♥. At MP, 11 + 12 + 3 + 2 = 28 > 26 + 0 - 0 = 26 so I'd double. At teams it is 28 on the LHS but now 26 + 2 - 0 = 28 on the RHS so I'd be on the border and pass.

You hold Kxx Kxx Kx Kxxxx and partner opens a 10-12 1nt. Your opponents end up bidding to 3♦. At MP, 12 + 10 + 2 + 2 = 26 > 26 + 0 - 3 = 23 so I'd double. At teams the 26 stays on the LHS but the RHS is now 26 + 2 - 3 = 25 so I'd still double.

Basically if they have an 8 card fit at the 2 level then in MP I want partner and I to have a minimum of 22 points, and at teams an extra margin where we have a minimum of 24. If they have an 8 card fit at the 3 level, I'm now ok with us having just 20 points at MP, but want 22 at teams. If they are at the 3 level with the 9 card fit, I now need 21 points at MP, 23 at teams.

I played a lot of weak and mini nt and so had a lot of chances to observe overcalls and I think the formula works. It is hard to sim it to tell for sure, since it matters what qualities you use for overcalls, and in practice those are quite wide ranging and varied across the population.

[dake50]

Don't miss your 500/800+ bonanzas.
Yu18772 must continue the 500/300 vs 100/50, etc.

[Yu18772]

dake50, on 2011-November-19, 22:23, said:

Don't miss your 500/800+ bonanzas.
Yu18772 must continue the 500/300 vs 100/50, etc.

If you stand to gain 500/800 its hardly a close double...the question was about if you are unsure that they are going down, not if you are unsure how many.
Also, at top levels its very uncommon that opponents volunteer for such a number (unless they sac against likely slam).

[Zelandakh]

When I was young the Rule of 10 and 12 referred to 3rd and 5th opening leads! lol. The rule I learned for, for example, passing partner's negative double was the Rule of 9. I long ago abandoned sticking to any rule in these spots and just try to imagine the other hands and decide if we are beating the contract or not and what we might be making. On the other hands these rules can be nice starting points sometimes, especially when working with very limited information.

[FrancesHinden]

I also hadn't heard of the rule of '10' or '12'. I asked my husband and he suggested that the 'rule of 10 and 12' was "don't double the opponents in a partial if they are going to make 10 tricks, unless they are cold for 12 in which case it might be a good result against slam"

I think you aren't watching enough good players if you think doubled partscores don't exist. Even at imps, you are going to concede the occasional making contract.
A better guide for doubling low-level contracts is whether you have anything that's surprising. Having AQx of trumps won't necessarily surprise the opponents, they knew they were missing these when they bid. Having QJ1098 is a surprise, because they would have been hoping the suit was 3-2 not 5-0.

[TheoKole]

My apologies, I thought that the rules of 10 and 12 were well known.

It goes like this,

The best part score doubles occur when 3 conditions are present.

1) A misfit with partners hand.
2) Having a preponderance of high card points for your side
3) You or your partner have length and strength in their trump suit. (Length can be a combination, strength needs to be in one hand)
For example partner opens 1 NT, RHO overcalls; you can add partners known length (2 cards) to your length.

Rule of 10 deals with trumps strength and the Rule of 12 deals with trump length. How much do you need?

Rule of 10: 10 - number of contract tricks = number of trump tricks needed

Rule of 12: 12 - number of contract tricks = number of trumps needed

How many tricks have they contracted for? Level 1 = 7, level 2 = 8, level 3 = 9

ex. against 3 ♦ = 9 tricks

Rule of 10: 10 - 9 = 1 trump trick needed (a modification also exists that if you are in front of declarer you need 1 extra trump trick)

Rule of 12: 12 - 9 = 3 trumps needed

Trump tricks are self explanatory, trump length is needed because the less trumps that declarer has, means the more off-suit cards he will have, which will mean that partners high cards will pull more weight and take more tricks.

How exactly do you calculate trump tricks?

You assume that declarer will play trumps from the top and you calculate how many tricks that will give you, add an extra trick for any trumps over 4

You have KQJxx, in trumps calculate 3 + 1 = 4 trump tricks, obviously you want to ruff 1 time.

You have QJx, calculate 1 trump trick

You have QJ9xx calculate 3 tricks (in this example do not calculate +1 for trump length - it will be taken up by the AK of trumps the spots may play a factor)

Your specific trump holding will probably indicate the defense that you want to follow also.


The rules of 10 and 12 also exist for 3/5 leads but are a separate part of the game.

Thanks for the comments,

Theo