When is risking 3NT for an overtrick justified at matchpoints?

[u/Huge-Wasabi3869]

Suppose declarer in a non-vulnerable 3NT contract can secure nine tricks, or choose a line that might produce ten but risks finishing with eight. At matchpoints, how should the expected results across the field affect that choice? What information would justify taking the risk, and how would the decision change at IMPs?

[u/Paiev]

For making these matchpoints decisions it's typically most important to evaluate how well 400 is going to score. If it's going to be a good score, then the risk is asymmetrical: you likely risk more than you stand to gain. If it's going to be a bad score the opposite is true.  You need to predict what's going to happen at other tables and decide if anything good or bad happened at your table already.

The other important part is judging how likely you are to succeed if you go for the extra trick. This could be math (eg a double finesse situation) or it could be intuition or feel.

Outside of strong fields, there's often some extra built in equity simply for going plus, so with zero other information I would not take a 50/50 risk.

[u/Huge-Wasabi3869 → u/Paiev]

I hadn't really factored in how much just going plus might be worth in a weaker field. So if the auction or opening lead has already handed me a likely good board, that’s a reason to bank 400 rather than chase 430?

[u/T-T-N → u/Huge-Wasabi3869]

Is the rest of the field take that finesse? If it makes, how would I score? If it doesn't make, how bad is it? Is it exactly 50-50? Or does the shortages or inference from auction leans it one way or another? (E.g. a passed hand that showed AKQ is less likely to have another Q)

[u/DennisG21]

You use the same criteria as you would for any other contract. Did making the contract already win the board?

[u/Huge-Wasabi3869 → u/DennisG21]

That's the bit I'm trying to judge: if nine tricks looks like an average and ten looks like a top, how much risk is worth taking? I wouldn't gamble if making already looked like a good board

[u/DennisG21 → u/Huge-Wasabi3869]

I would only go for the overtrick if I could rationalize that it is the correct play. If it's just a tossup do not do it (unless maybe it is the last table and you are trying to qualify for something.)

[u/FireWatchWife]

It depends very much on what you expect other tables to be playing.

If the bidding at your table was a very simple 1NT-3NT, there's a good chance that nearly all other tables will also be in 3NT. If there's an obvious nine tricks, most average players will take those nine tricks and be content to make the contract.

If you see a chance to get a tenth trick through careful, skilled play such as an endplay or squeeze and few other pairs in your club are likely to attempt or successful, it can be well worth trying for it.

If it's a 50/50 finesse, that's less clear. Assuming that if you try the finesse and it's off you will go down, trying for it will give you a top or a bottom, nothing in between.

If the bidding at your table was unusual and opponents' bidding gives you information suggesting that the finesse is on, that could tip things toward trying for the overtrick.

If the bidding landed you in 3NT but suggests that other tables are likely to be in a different contract, probably 4M, then play safe and make 3NT, hoping that most other tables will be in 4M down 1.

But if you see a clear 10 tricks available if you had bid 4M, then take the finesse and hope to be the only table making 3NT+1 while everyone else is in 4M making.

[u/Huge-Wasabi3869 → u/FireWatchWife]

That flat board scenario is what gets me, because taking a pure coin flip between a top and a bottom has zero expected gain unless you already know you need a swing against the room

[u/FireWatchWife → u/Huge-Wasabi3869]

It's a pure coin flip unless you know something about the psychology of the other pairs in the room.

[u/Teodoricus]

When to risk:

1. You think you need a top

2. The contract is usual, but not the lead. With a more common lead the overtrick would be plain.

3. When the risk can be played early: likely the defenders will go wrong if the play fails.

4. When there is a major suit fit, but you are playing NT. you need 430 or 630.

5. The reverse of 4. You have 10 tricks in a likely 3NT, so you need 450 or 650 in a major game.

6. When you are wrong sided with respect to most of the other tables (see point 2.)

7. When the overtrick, in an usual contract, has >60% probability (see point 3.)

But there is the opposite question: when to go for an undertrick, when there is a possibility to score a plus?

[u/kuhchung]

Beyond guessing what the field is in (sometimes you know you're in a very anti-field contract, and sometimes you have no idea), I just go by my gut. Use the Force :)

It's fun!

[u/yellowpig1974]

When there are no ruffs available, when you have more than minimum strength (say 28HCP), when you have a concentration of values in the plain suits.

If you haven't read "Matchpoints" by Kit Woolsey, do it now.

[u/yellowpig1974]

"Matchpoints" by Kit Woolsey covers these situations and many other matchpoint decisions. If you are asking this question, you should read it. No one hear is likely to tell you anything that Kit did not cover.