[shyams]

IMPs, huge field (day long on BBO)

You declare in 3NT after dealer opens a weak 2♥.

---

Trick 1: ♥Q - ♥A - ♦3 - ♥4
Trick 2: ♣A - ♣2 - ♣3 - ♣4
Trick 3: ♣7 - ♣5 - ???

Play the ♣9 or a top card? I thought about it for a bit, but I was unsure if my chosen action was correct.

[mw64ahw]

Likely shapes
2632
1633
If 5♣ is played then West has (xx)4
Clubs are likely split 4-2 or 3-3
Play for the T♣ to drop

[P_Marlowe]

Hi,

probability / statistics is not my strong forte as a mathematician, never was, anyway:

The finesse is protecting you against the 5-1, which would imply a 6-?-?-1 distribution,
the a prioriy prob. for a specific 4-2 / 3-3 split is 85%, which means, you would protect
yourself against a 7-15% scenario at best, I think we can rule out 65.

The gained information does not add. anything to change this, but the existence of a 6 carder
with west does.
https://en.wikipedia...e_probabilities

Vacant places will tell you, that the T is with 6:11 with East, i.e. approx. 33%, ..., i.e.
the finesse wins in 2 out 3, but in lots of cases, the finesse would win, when drop would also win.

This is as far as I came.

...

I would not be surprised, if the finesse is roughly equal to playing for the drop, but the drop
is easier to explain, and the longer I think about it, the more the drop gains, hedging my bets.

With kind regards
Marlowe

I think this is easier to simulate than to calculate, esp. given that the card we are interested in,
has no HCP at all, and will not really play a role in deciding to (not) open a W2.

[pescetom]

At the table I can't simulate and I can't see an easy calculation beyond vacant spaces (6:11 = 54%) either, which is not much help. FWIW I would go for the drop at table, my instinct says that West 6-4 is more likely than West 6-1.

I'll simulate later if I find time.

[Cyberyeti]

Need to check what a first seat weak 2 looks like and whether they can have 4 spades and whether they have an Ekren 2♦ and whether they use it 6-4. Also their arrangements on what a double of 3N would say from the non opener.

You may be able to rule some shapes/holdings out

[P_Marlowe]

Cyberyeti, on 2026-October-20, 04:40, said:

Need to check what a first seat weak 2 looks like and whether they can have 4 spades and whether they have an Ekren 2♦ and whether they use it 6-4. Also their arrangements on what a double of 3N would say from the non opener.

You may be able to rule some shapes/holdings out

If you rule out 64 in the majors, for whatever reasons, which is valid (you could rule out max. with 6-4, even without special agreement)
expected club length goes up, implying drop gains.

[Cyberyeti]

P_Marlowe, on 2026-October-20, 04:58, said:

If you rule out 64 in the majors, for whatever reasons, which is valid (you could rule out max. with 6-4, even without special agreement)
expected club length goes up, implying drop gains.

This was my point, if X from RHO says "don't lead your suit" we can probably rule out solid running diamonds.

[pescetom]

I calculated it quickly from the probability of distributions 6322 6421 6430 6511 6520 and the permutations for 1,2,3,4,5 clubs and it looks like the drop succeeds about 84% (excluding things like not opening 2H with spades) which is enough for me.

[P_Marlowe]

pescetom, on 2026-October-20, 07:00, said:

I calculated it quickly from the probability of distributions 6322 6421 6430 6511 6520 and the permutations for 1,2,3,4,5 clubs and it looks like the drop succeeds about 84% (excluding things like not opening 2H with spades) which is enough for me.

This is basically the a priory prob., without taking into account the information, that you collected,
your calc is correct, or wikipedia is correct, my take is, your calc and the calc that the number of
wikipedia are based on are independ

[mw64ahw]

The problem is if you get the finesse wrong then suddenly you lose a whole load of diamonds and may get a worse score than those taking the available tricks.

[Cyberyeti]

mw64ahw, on 2026-October-20, 07:10, said:

The problem is if you get the finesse wrong then suddenly you lose a whole load of diamonds and may get a worse score than those taking the available tricks.

It's IMPS and they're only 50s

[pescetom]

P_Marlowe, on 2026-October-20, 07:04, said:

This is basically the a priory prob., without taking into account the information, that you collected,
your calc is correct, or wikipedia is correct, my take is, your calc and the calc that the number of
wikipedia are based on are independ

Well it takes account of the three small clubs played, but nothing more.
I strongly doubt that the inferences about spades in West from 2H or about spades and diamonds from the 3D discard by East are enough to change the decision.

[pescetom]

mw64ahw, on 2026-October-20, 07:10, said:

The problem is if you get the finesse wrong then suddenly you lose a whole load of diamonds and may get a worse score than those taking the available tricks.

If the drop fails you are in much the same boat, East is bound to return a diamond given the auction and dummy and West will probably have discarded spades.
In any case it's IMPS, as others said.

[P_Marlowe]

mw64ahw, on 2026-October-20, 07:10, said:

The problem is if you get the finesse wrong then suddenly you lose a whole load of diamonds and may get a worse score than those taking the available tricks.

The question was, if the add. information about the specific layout of the given deal, given the auction and the first played rounds,
is enough to overrule the default play, which is playing for the drop.
The drop will work 85% of the time for all deals, but we are looking at a specific restricted set of deals.

I now think stronger than before, that the drop is superior, ..., but it is likely closer as one may expect.

[shyams]

The actual deal was benign. Either action would have worked; West had ♣84

I am not good at these calcs at the table. I thought that it was a close thing and I was tempted to finesse.

However, I did play the ♣ honour at trick 3. One can bemoan one's luck when suits break 5-1 but it's much harder to justify losing to a doubleton ♣10 (psychology?)

---

[gszes]

pescetom, on 2026-October-20, 07:00, said:

I calculated it quickly from the probability of distributions 6322 6421 6430 6511 6520 and the permutations for 1,2,3,4,5 clubs and it looks like the drop succeeds about 84% (excluding things like not opening 2H with spades) which is enough for me.

redo your calculations to account for lho clubs being either 2 3 or 4 (if they had 1 it showed up on the first club play) (once rho follows to the second club it is impossible for lho to hold 5) and you will have a pretty decent approximation.

[pescetom]

gszes, on 2026-October-24, 14:23, said:

redo your calculations to account for lho clubs being either 2 3 or 4 (if they had 1 it showed up on the first club play) (once rho follows to the second club it is impossible for lho to hold 5) and you will have a pretty decent approximation.

I wouldn't have worried at the table and I don't worry in front of the rough numbers either, although I would like BBO to restore the Tricks function to Dealer so that I could simulate accurately.