[Cyberyeti]

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W leads a diamond from Qxxx, they cash 4 diamonds, W switches to 6♠ (top of doubleton, second from 3 or more small cards), plan the play.

This is an innocent little hand but there is one thing you should not do which is what our declarer did.

A/E please spoiler your answers until some beginners have had a go.

[eagles123]

What I would do is win the spade and cash a second spade to try and see if west started with a doubleton or 3 +. After that I'm struggling to see how its any more than a guess on the clubs. I guess if spades are west 2 east 5 then west is more likely to have the Q club so probably finesse that way but if it's (34) then it seems like a guess? another think i would probably do is if West showed 3 or more is then cash a third spade incase its now west 5 east 2 to play east now for CQ although that obviously requires West to have x6789 of spades which is quite a long shot

[1eyedjack]

Spoiler

I don't think that this is trivial for a beginner, and of course whatever you do does not come with guarantees. We are just looking to maximise our chances, and those chances of course hinge on picking up the Clubs without loss.

*If* you just look at the Club suit in isolation and ignore any additional information, then the percentage play would be to cash the Club King (to cater for a singleton Queen), and then when all follow low finesse West for the Q. This picks up queenleton offside and Q(x(x(x))) onside. Were you to try to cater for East having the Queen, you could EITHER take a first round finesse, which picks up Qxxx onside but loses to Queenleton offside, OR you could cash the Ace first before finessing, which would pick up Queenleton offside but you could not pick up Qxxx onside.

If for some bizarre reason you had good reason to think that East held 4 Clubs (and you don't here), then the right play would be to take a first round finesse against East (rather than first cashing the Ace). Qxxx with East and x with West is 4 times more likely than xxxx with East and Q with West. There are 4 "x"s that West might hold as singleton but only one Q.

So, purely in terms of the number combinations that you can pick up, cashing the King and then finessing against West comes out a winner, by the thickness of a hair.

But a Queenleton has a very small probability. It can happen, and if there is nothing else to go on and if there are no downsides (such as losing the opportunity to pick up Qxxx in the other hand) then you might as well play to cater for it. But it is a small probability nevertheless, and there may be other indicators that do not require you to look at the basic odds in a vacuum.

The first question to ask yourself is why did West lead a Diamond at all, from Qxxx? N/S have made no attempt to find a Major suit fit. Unless you are GIB (which has a tendency to lead shortages against NT, sometimes bizarrely, but with uncanny accuracy), you would tend to favour a major suit lead given half an excuse (such as equal or greater length). So while it is by no means certain there is a reduced likelihood of West holding a 4 card (or longer) major, given his decision to lead from a 4 card Diamond suit.

If West has at most 3-3 in the majors, and is known to have only 4 Diamonds, then to make up a hand of 13 cards he must have at least 3 Clubs, giving East therefore at most 2 of them. This observation gives a greater than 50% chance that West has the Q.

Perhaps of some interest is that with Qxxx in both minors, and with nothing in the bidding to go on, if he is committed to leading one of the minors he has a 50-50 guess which to lead. The fact that he chose to lead a Diamond therefore reduces (by half) the chances of his having started with Qxxx of Clubs. Even so, he might have held xxxx or Qxx, both of which you can pick up by cashing the K and then finessing.

You might be able to refine your odds a bit by cashing some major suit winners in case someone shows out, but you will want to keep an entry to the Clubs just in case something bizarre happens to indicate playing East for the Club length. Personally I wouldn't bother.

So it took a while to get there, but I conclude that the "isolationist" route of cashing the King and then finessing is if anything reinforced by the other information provided in the play so far. After all that I fully expect someone to come up with a reason why this is all baloney.

[suleiman22]

Sorry if I sound like I have never used a computer before- how do I spoiler my answer? Cannot seem to figure it out- new to the site.

[1eyedjack]

 suleiman22, on 2013-September-23, 17:43, said:

Sorry if I sound like I have never used a computer before- how do I spoiler my answer? Cannot seem to figure it out- new to the site.

No worries. It is not obvious. One way to find out how is by drafting (without posting) a reply to a specific post which does already contain a spoiler. You do that not by clicking on the quick reply button, nor the main reply button at the foot of the screen. But each individual post has a reply button in the bottom right corner of the post. Click on that and it opens up a draft reply window that already contains within it the earlier selected post including encoded formatting such as spoiler settings. This exercise shows that to include a spoiler you add the word "Spoiler" at the beginning and "/Spoiler" at the end but substitute square brackets where I have just used double quote marks.

[Cyberyeti]

 suleiman22, on 2013-September-23, 17:43, said:

Sorry if I sound like I have never used a computer before- how do I spoiler my answer? Cannot seem to figure it out- new to the site.

Easiest way, type in the text you want to spoiler, highlight it, go to the pulldown menu under "other styles" select spoiler. Or just select spoiler from that menu before typing your text which will give you the start/end tags and type your stuff between them.

[Cyberyeti]

As nobody else is commenting after 1eyedjack gave that very comprehensive answer, I'll explain what I was getting at (which they covered).

There is the potential for a "The operation was a success but the patient died" situation. If you decide E has Q♣, you should not cross to A♣ then lead towards the J, but should cross in a side suit and run the 10. Why ? well it doesn't matter if they're 3-2, but if they're 4-1 playing the A first caters for W's singleton being the Q, running the 10 caters for any of the 4 small singletons so is much more likely to succeed.