[SimonFa]

I hate these decisions..

WvR, MPs

♠AQ532
♥K6
♦832
♣432

1NT (p) 2H (p)
2S (p) ?

Now what?

We play a style that never upgrades or downgrades into NT so 15-17 HCP is honest.

Normally on 9HCP and this vulnerability I would look to go to 3NT with 9HCP but all those little cards aren't very promising, even the 5 card spade suit doesn't fill me with enthusiasm.

In the end I took the 2NT route but in the knowledge that partner doesn't take much to accept an invite. With T98's I would have gone straight to 3NT

So a cowardly bid or pragmatic?

As a matter of interest, I've not seen anything on the distribution probability of HCP; what is the probability of partner having 15, 16 or17 HCP? Is it more likely that they will have 15 rather than 16 or 17? Or put another way, do the odds favour bidding 3NT with 9HCP?

Spoiler

Partner went to 3NT and made the contract - she had ♣AKQJT! - and made 10 tricks for 13/15

[Porreankel]

I think you did fine!
You have othing more than promised with a 2nt bid - and you rp can easily decide whats best from here.
Not even in IMP would I have bid different - so well done.

http://bridgetime.org/

[hrothgar]

SimonFa, on 2011-September-13, 06:47, said:

As a matter of interest, I've not seen anything on the distribution probability of HCP; what is the probability of partner having 15, 16 or17 HCP? Is it more likely that they will have 15 rather than 16 or 17? Or put another way, do the odds favour bidding 3NT with 9HCP?

I consider bidding 3N clear cut.

With respect to the PDF of partner's HCPs. Here's what I came up with using a quick monte carlo sim

Partner is always much more likely to have 15 HCPs than 16; however, when you hold 9 HCPs the odds are even more skewed towards partner holding a 15 count.

    Points    Unconstrained    Constrained
     0        0.00359          0.00084    
     1        0.00759          0.00338    
     2        0.01363          0.00717    
     3        0.02414          0.01465    
     4        0.03905          0.02542    
     5        0.05187          0.03912    
     6        0.06586          0.05503    
     7        0.08084          0.07007    
     8        0.08861           0.0849    
     9        0.09319           0.0959    
    10         0.0954          0.10055    
    11        0.09017          0.09698    
    12        0.08004          0.09214    
    13        0.06724          0.08049    
    14        0.05687          0.06816    
    15        0.04461           0.0548    
    16        0.03307          0.03928    
    17        0.02367           0.0281    
    18          0.016          0.01847    
    19        0.01026          0.01148    
    20        0.00628          0.00655    
    21        0.00403          0.00363    
    22        0.00217           0.0017    
    23        0.00085          0.00066    
    24        0.00055          0.00037    
    25        0.00029          0.00011    
    26         7e-005           3e-005    
    27         2e-005           1e-005    
    28         1e-005           1e-005    
    29         3e-005                0    
    30              0                0    
    31              0                0    
    32              0                0    
    33              0                0    
    34              0                0    
    35              0                0    
    36              0                0    
    37              0                0    
    38              0                0    
    39              0                0    
    40              0                0    


Points = zeros(39,1);
Points(1:3) = 4;
Points(4:6) = 3;
Points(7:9) = 2;
Points(10:14) = 1;

%% shuffle

simlength = 100000

MC_Result = zeros(simlength, 1);

for i = 1:simlength
    
    index = randperm(39);
    Points = Points(index);
    MC_Result(i) = sum(Points(1:13));
    
end
    
mean(MC_Result)   

Output = 0:40;
Output = Output';

for i = 1:41

    Output(i,2) = length(MC_Result(MC_Result == i-1));
    
end

Output

[aguahombre]

Forum posters who have opened 1NT (15-17) have pretty much agreed in the past that they (we) accept invites on the vast majority of 16's and even some 15's. If playing with a forum poster, the invite was fine.

The important thing about charting the probabilities on whether partner has a good 1NT opener or a bad one is this: she gets to look at her hand when invited, so we don't have to guess whether to bid game all by ourselves.

[mgoetze]

SimonFa, on 2011-September-13, 06:47, said:

WvR, MPs

[...]

Normally on 9HCP and this vulnerability I would look to go to 3NT with 9HCP

I don't quite understand... white at Matchpoints is not the situation where you need to look for games very aggressively! I think 2NT is perfectly normal.

SimonFa, on 2011-September-13, 06:47, said:

As a matter of interest, I've not seen anything on the distribution probability of HCP; what is the probability of partner having 15, 16 or17 HCP? Is it more likely that they will have 15 rather than 16 or 17?

15 HCP 44%
16 HCP 33%
17 HCP 23%

(100,000 simulations, no 5-card majors in 1NT)

[mgoetze]

In case anyone cares, I suppose I'll show my work too

source /usr/share/deal/format/none

south is "AQ532 K6 832 432"

set fifteen 0
set sixteen 0
set seventeen 0

main {
	if {![balanced north]} {reject}
	if {[hcp north] == 15} {
		set fifteen [expr $fifteen + 1]
		accept
	}
	if {[hcp north] == 16} {
		set sixteen [expr $sixteen + 1]
		accept
	}
	if {[hcp north] == 17} {
		set seventeen [expr $seventeen + 1]
		accept
	}
	reject
}

deal_finished {
	puts "15 HCP: $fifteen"
	puts "16 HCP: $sixteen"
	puts "17 HCP: $seventeen"
}

% deal -i hcp.tcl 100000
15 HCP: 44138
16 HCP: 32855
17 HCP: 23007

[pooltuna]

invite at MP go to game if V at IMPS

[hrothgar]

mgoetze, on 2011-September-13, 07:21, said:

In case anyone cares, I suppose I'll show my work too

I, for one, think its useful to show the scripts that people use to generate sims.

Its the easiest way to check assumptions and for correctness.
And who knows, it might help inspire folks to learn a new skill.

FWIW, I reran my sim (generating a million hands)

My estimates for the relative frequency of 15:17 was essentially identical to Michael's

15 HCP = .4426
16 HCP = .3282
17 HCP = .2292

Going back to the real question:

I still think that bidding 3N is pretty clear.
I'll be interested to see whether the consensus changes once Justin gets dragged in.

[gwnn]

Looks like a clear 3N. Prime 9 count. Yes, there's not so many intermediates, but what can you do..

[Free]

gwnn, on 2011-September-13, 07:58, said:

but what can you do..

Invite

Personally I don't have strong feelings about this decision. If you know your partner will accept light, then 2NT seems fine to me.

[billw55]

Interesting. To my eye this is an open and shut invite, I did not expect anyone to advocate a direct 3NT. And yet there they are.

The biggest consideration to me:

aguahombre, on 2011-September-13, 07:10, said:

The important thing about charting the probabilities on whether partner has a good 1NT opener or a bad one is this: she gets to look at her hand when invited, so we don't have to guess whether to bid game all by ourselves.

Right. Why on earth would I care what the probabilities are of 15 v. 16 v. 17? My partner already knows what he holds. I expect him to accept with any 17; or with 16 and any bonus feature (such as a five card suit, working ten, Hx of spades, high honor quality); or even with an exceptional 15.

Bidding 3NT myself is just anti partnership.

[SimonFa]

mgoetze, on 2011-September-13, 07:14, said:

I don't quite understand... white at Matchpoints is not the situation where you need to look for games very aggressively!

That's where I'm going wrong.

[ggwhiz]

A lot depends on the rest of your methods.

We super accept the transfer aggressively with either 2nt or 3♠ so bidding 2nt here is plenty for us.

That invitation is also accepted aggresively by opener so 3nt would be a hang job.

Note: Just looked at the spoiler and at these colours and with those clubs we might open 1nt with some real cheese in the other suits.

[aguahombre]

ggwhiz, on 2011-September-13, 10:00, said:

Note: Just looked at the spoiler and at these colours and with those clubs we might open 1nt with some real cheese in the other suits.

But, I bet you would accept an invite with that; I would, and it would just make partner's blast to 3NT on his hand irrelevant and also annoying whether it makes or not.

[gwnn]

Anti partnership and annoying? I invite when I think I have an invite and I force to game when I think I have a game force. I don't see where the problem is. I admit I am somewhat biased against inviting, I tend to try to either stop low or force to game, but I am not doing this because I disrespect my partner or I try to annoy him. I just don't like declaring/being dummy in 2NT, the odds are against us.

This is not to say I never invite. I do invite when I think invitation is the best course of action. I don't think 3NT is clear here at all, it's just that I would bid 3NT.

[gwnn]

To the OP:

Quote

I hate these decisions..

you shouldn't hate these decisions. They don't matter in the long run. You can bid 2 or 3 NT and if you think it's very close, you can bid whichever you feel like. It really isn't a big deal.

[VM1973]

In my opinion this is a clear invite. In a plurality of cases your partner will have 15 HCPs. If he has more, he'll go.

[MrAce]

Imo you should ignore any reply that makes a long analysis and ends up saying this hand is CLEAR 2 NT or clear 3 NT. You know, i know and everyone else here knows the outcome of your decision in the long run will have very less to do with mastermind analysis of a 9 count 5332 hand vs a NT opener at mp. At imps you should bid game if you are not sure whether to bid game or invite by default.

[MickyB]

There is one non-obvious factor to take into consideration - for most, bidding 3NT will end the auction opposite a 3(433), but bidding 2NT will lead to 3S or 4S.

[Phil]

I'd invite.

The spotless spades are of questionable value if partner does not fit them. Do you really want to be in game with 15 (or even the upgraded 14) opposite a hand with a doubleton?

However if pard does take preference back to 3♠ then I will try 3N which I expect pard will sit for unless he has a ruffing value or maybe an open suit.

If I were to blast game I would have just bid 3N the 1st time which I expect to make a lot. I also think a spade lead is quite possible on this auction. Its great when this rides over to pard's Jx.

As an aside I play 1N - 2♣ - 2x - 2♠ as a weak invite so 2N shows a good invite which is exactly what this hand is.