Raptor

[Sigi_BC84]

Sure, you can run computer simulations that might say something interesting about the convention, but they will never be as decisive as a double dummy analysis of a play contract.

No they won't; apparently you took my remark regarding DD accuracy the wrong way. I'm not saying that you can easily (or at all) setup a simulation that will yield a quality hypothesis regarding the value of the Raptor convention.

 

I'm only saying that given you find a good simulator setup, DD accuracy will not be in your way when it comes to determining the actual trick value of a hand -- regarding real world play of that hand.

 

--Sigi

[Sigi_BC84]

Frances is right - the "raptor vs. 1NT" issue is FAR too complex to expect much help from present day software. In principle I

You and Frances are both correctly hinting at the complexity of this problem. Let me say though that I was not suggesting that you will find a "42 is the answer"-like result to the Raptor vs Natural question by using a deal generator and double dummy analysis.

 

I was thinking about solving some of the problems related to the subject, e.g. how dangerous is a natural NT overcall with regard to penalties, and how often do you find a playable partscore using Raptor that you would not have found otherwise (because of supposedly hidden major suit fits that come to light).

 

Maybe I'm being too naive about the problem and the complexities and inferences involved are too many so that answering questions like the above won't be of much value anyway. Hopefully I've brought my idea across at this point ;-).

 

--Sigi

[hrothgar]

What I'm having in mind is to construct typical deals where Raptor and natural notrump overcalls would apply, and see which one loses or gains more and if it will average out in the end.

For what is worth, I did graduate work in game theory...

I also think that i have a passing knowledge regarding different bidding systems...

 

While I find discussions like this one an interesting way to pass time, I'd strongly recommend against trying to do any "serious" work in this field. The topic is WAY too complex to reach anything resembling a definitive answer...

 

Francis has already alluded to three of the key problems in formal analysis of bidding systems:

 

The first is the relationship between the "bidding game" and "card play" game. All the different bids that you make (or don't make) have an important impact on declarer play and defense.

 

Equally significant, you can't analyze individual bids in isolation. Case in point, you can't hope to analyze Ben's Misery preempts without also consider the impact on the major suit opening style.

 

Finally, you need to consider the opponent's best responses. Unfortunately, many people who vreate a new toy often have significant blind spot's regarding different ways to exploit the methods.

 

To this list, I'd add one other issue. From my perspective, this is the real deal-breaker in that it increases the complexity of the problem by a couple orders of magnitude. As I've noted in the past, we have no reason to suspect that bidding systems exhibit transitivity. Assume that

 

2/1 Game Force is a "better" system than Acol

In a similar fashion, Precision is better than 2/1 Game Force

If transitivity holds true, then Precision is better than Acol...

 

My gut says that transitivity assumptions are not warranted, in which case we aren't looking for an optimal bidding system, but rather, some a population consisiting of some optimal ratio of bidding systems. Throw in the potential for cyclical equilibria and you have a modelling problem that I wouldn't touch with a 10 foot pole (unless, of course, I was being paid by the hour)

[pclayton]

The point I was making on the DD analysis thing is that it's not enough to take hands where you would have a Raptor 1NT overcall or a natural 1NT overcall. You have to take pretty much _all_ competitive auctions, because of the inferences available from the lack of use. I've never played Raptor, nor against it, so I'm not certain what these are, but I bet there are loads of them.

 

Then the opening side will (might) have a different defence to a Raptor 1NT overcall than a natural 1NT overcall, and might end in a different contract. Particularly relevant to DD analysis, if the opening side declarer the hand they will have different information about the opposition layouts: a natural 1NT overcall gives a blueprint to the declarer play that DD analysis won't give Raptor the benefit of (and vice versa but in different final contracts and possibly to a different overall extent).

 

I agree it could be done, but I think it's a seriously large amount of effort.

No, I think that you were right the first time, it can't be done.

 

Sure, you can run computer simulations that might say something interesting about the convention, but they will never be as decisive as a double dummy analysis of a play contract.

When I first started playing Overcall Structure, I kept pretty detail logs on my MP results every time a systemic call would come up and tried to stay objective about whether or not the actual method created the result or just good (or poor) judgement.

 

With Power Doubles, its pretty easy to see where we pick up; when the strong hand is put on lead and the lead comes around to the responder of the power doubler; when we get to nail the opponents at the 1 level for +800, and the like. These results have NOTHING to do with judgement; they are borne out of the use of the convention.

 

With 1NTO, results are more difficult to judge. If we get murdered in a misfit, it must be in the context of "what happened to those that made a takeout x (or passed)"? Or, if we are able to jam their auction and more effectively judge the starin / level, it must be in relation to what a takeout doubler did as well.

 

Nevertheless, these results are at best anecdotal.

 

With Raptor, many times the 4-4 (supposedly) side fit usually gets buried, unless overcaller has substantially extra values. I think it might be easier than you think to run Bridgebrowser and pull out 1N overcalls that contain 4M (or other major) / 5+ minor (or other minor), and determine how effective the convention was. A side singleton / void would also be a telltale sign that a pair was using the convention.

 

Even though the IMP / MP result can't be directly correlated to the mere presence of the convention, it would still be useful to know what the aggregate result would be using these methods.

[fred]

The point I was making on the DD analysis thing is that it's not enough to take hands where you would have a Raptor 1NT overcall or a natural 1NT overcall. You have to take pretty much _all_ competitive auctions, because of the inferences available from the lack of use. I've never played Raptor, nor against it, so I'm not certain what these are, but I bet there are loads of them.

 

Then the opening side will (might) have a different defence to a Raptor 1NT overcall than a natural 1NT overcall, and might end in a different contract. Particularly relevant to DD analysis, if the opening side declarer the hand they will have different information about the opposition layouts: a natural 1NT overcall gives a blueprint to the declarer play that DD analysis won't give Raptor the benefit of (and vice versa but in different final contracts and possibly to a different overall extent).

 

I agree it could be done, but I think it's a seriously large amount of effort.

No, I think that you were right the first time, it can't be done.

 

Sure, you can run computer simulations that might say something interesting about the convention, but they will never be as decisive as a double dummy analysis of a play contract.

When I first started playing Overcall Structure, I kept pretty detail logs on my MP results every time a systemic call would come up and tried to stay objective about whether or not the actual method created the result or just good (or poor) judgement.

 

With Power Doubles, its pretty easy to see where we pick up; when the strong hand is put on lead and the lead comes around to the responder of the power doubler; when we get to nail the opponents at the 1 level for +800, and the like. These results have NOTHING to do with judgement; they are borne out of the use of the convention.

 

With 1NTO, results are more difficult to judge. If we get murdered in a misfit, it must be in the context of "what happened to those that made a takeout x (or passed)"? Or, if we are able to jam their auction and more effectively judge the starin / level, it must be in relation to what a takeout doubler did as well.

 

Nevertheless, these results are at best anecdotal.

 

With Raptor, many times the 4-4 (supposedly) side fit usually gets buried, unless overcaller has substantially extra values. I think it might be easier than you think to run Bridgebrowser and pull out 1N overcalls that contain 4M (or other major) / 5+ minor (or other minor), and determine how effective the convention was. A side singleton / void would also be a telltale sign that a pair was using the convention.

 

Even though the IMP / MP result can't be directly correlated to the mere presence of the convention, it would still be useful to know what the aggregate result would be using these methods.

I think you are suggesting that you measure:

 

0) The expected IMP/MP gain or loss when a Raptor 1NT overcall is made

 

This will only be meaningful if you also measure:

 

1) The expected IMP/MP gain or loss when natural 1NT overcall is made

2) The expected IMP/MP gain or loss when a pair playing Raptor is dealt a hand suitable for a natural 1NT overcall

3) The expected IMP/MP gain or loss when a pair playing natural 1NT overcalls is dealt a hand for Raptor

4) The relative frequency of hands appropriate for Raptor versus hands appropriate for natural 1NT overcall

 

I suspect that 2) and 3) would be hard to extract from BridgeBrowser.

 

To really do this properly, it would likely be appropriate to consider all dealer/vul combinations separately (and perhaps conclude that, for example, Raptor is a winner only if you are not vulnerable).

 

In addition, you should make an effort to study the average skill levels of pairs playing Raptor versus those that play natural 1NT overcalls.

 

Even then, it is hard to say if this would really prove anything.

 

Impressed by your dedication to research! Great that you take notes and study the gains/losses of your conventions.

 

Fred Gitelman

Bridge Base Inc.

www.bridgebase.com

[kenrexford]

This sort of analysis should be used more frequently. I ran a study for a few years on weak two bids. Simple bid, but amazing results.

 

First, I found that we ended up well above average on weak two bids by not opening weak twos.

 

Second, I found that we scored only two below-average results for these years on hands where we did not open a weak two but could.

 

Third, I found that weak two's came up rather infrequently.

 

Fourth, it appeared that the result on hands where a weak two was opened, if a weak two was opened, was determined by the opponents; hence, a weak two transfers control over the result to the opponents.

 

Fifth, alternatives to weak two's, even simple ones, resulted in many more gains than losses.

 

So, I found out that weak two's are bad bridge. Then, I started playing weak two's again. :D

[pclayton]

The point I was making on the DD analysis thing is that it's not enough to take hands where you would have a Raptor 1NT overcall or a natural 1NT overcall. You have to take pretty much _all_ competitive auctions, because of the inferences available from the lack of use. I've never played Raptor, nor against it, so I'm not certain what these are, but I bet there are loads of them.

 

Then the opening side will (might) have a different defence to a Raptor 1NT overcall than a natural 1NT overcall, and might end in a different contract. Particularly relevant to DD analysis, if the opening side declarer the hand they will have different information about the opposition layouts: a natural 1NT overcall gives a blueprint to the declarer play that DD analysis won't give Raptor the benefit of (and vice versa but in different final contracts and possibly to a different overall extent).

 

I agree it could be done, but I think it's a seriously large amount of effort.

No, I think that you were right the first time, it can't be done.

 

Sure, you can run computer simulations that might say something interesting about the convention, but they will never be as decisive as a double dummy analysis of a play contract.

When I first started playing Overcall Structure, I kept pretty detail logs on my MP results every time a systemic call would come up and tried to stay objective about whether or not the actual method created the result or just good (or poor) judgement.

 

With Power Doubles, its pretty easy to see where we pick up; when the strong hand is put on lead and the lead comes around to the responder of the power doubler; when we get to nail the opponents at the 1 level for +800, and the like. These results have NOTHING to do with judgement; they are borne out of the use of the convention.

 

With 1NTO, results are more difficult to judge. If we get murdered in a misfit, it must be in the context of "what happened to those that made a takeout x (or passed)"? Or, if we are able to jam their auction and more effectively judge the starin / level, it must be in relation to what a takeout doubler did as well.

 

Nevertheless, these results are at best anecdotal.

 

With Raptor, many times the 4-4 (supposedly) side fit usually gets buried, unless overcaller has substantially extra values. I think it might be easier than you think to run Bridgebrowser and pull out 1N overcalls that contain 4M (or other major) / 5+ minor (or other minor), and determine how effective the convention was. A side singleton / void would also be a telltale sign that a pair was using the convention.

 

Even though the IMP / MP result can't be directly correlated to the mere presence of the convention, it would still be useful to know what the aggregate result would be using these methods.

I think you are suggesting that you measure:

 

0) The expected IMP/MP gain or loss when a Raptor 1NT overcall is made

 

This will only be meaningful if you also measure:

 

1) The expected IMP/MP gain or loss when natural 1NT overcall is made

2) The expected IMP/MP gain or loss when a pair playing Raptor is dealt a hand suitable for a natural 1NT overcall

3) The expected IMP/MP gain or loss when a pair playing natural 1NT overcalls is dealt a hand for Raptor

4) The relative frequency of hands appropriate for Raptor versus hands appropriate for natural 1NT overcall

 

I suspect that 2) and 3) would be hard to extract from BridgeBrowser.

 

To really do this properly, it would likely be appropriate to consider all dealer/vul combinations separately (and perhaps conclude that, for example, Raptor is a winner only if you are not vulnerable).

 

In addition, you should make an effort to study the average skill levels of pairs playing Raptor versus those that play natural 1NT overcalls.

 

Even then, it is hard to say if this would really prove anything.

 

Impressed by your dedication to research! Great that you take notes and study the gains/losses of your conventions.

 

Fred Gitelman

Bridge Base Inc.

www.bridgebase.com

 

Yes, and more so:

 

As far as the gains / losses from the lack of a natural 1N overcall, they need to be dealt in the context of "what happened to the pair that couldn't overcall 1N". Did the action as a result of:

 

(1x) - double - (?) - 1y

(pass) - 1N....

 

get the opponents off to a better lead than the pairs that just overcall 1N?

 

Or did the auction proceed so that the pair playing Raptor couldn't 'control' the auction, by lack of a natural 1N overcall, like.....:

 

(1x) - double - (2x) - 2y

(pass / 3x) - ?...

 

where the balanced 15-17 could not effectively convey strength.

 

Or, did the pair playing Raptor somehow exploit the opponents with a low-level double since THEY could not adequately judge the auction.

 

Many permutations here.

 

All in all, while research is not my forte, I would think that there is enough variability in each case that the instances where a Raptor situation comes up the cases need to be dealt with on a case by case basis and a qualitative analysis be performed.

 

However, using BridgeBrowser could be the means to at least cull the hands and come up with a sample.

[Gerben42]

So, I found out that weak two's are bad bridge

 

Ssh... don't tell anyone!

[whereagles]

So, I found out that weak two's are bad bridge

 

Step outside and say that! :angry: ;) :P :wub:

[coyot]

Raptor fan here :angry: (Although I know it by the name of Polish NT).

 

When comparing the merits of natural 1NT overcall and Raptor, you should take frequencies of both bids into consideration.

 

Strong NT does not happen that often. Note that 16-18 is definitely less than half as frequent as 15-17 (and many people playing 15-17 openings still prefer 16-18 overcall).

 

On the other hand, Raptor can occur on most frequent HCP ranges (8-15(17)) and it's benefits also include hands where partner overcalls in 2m, denying major 4card. The negative inferences can be quite helpful when it comes to it.

 

My humble opinion could be thus summed up as:

 

1) Raptor comes in handy for many partscore battles

 

2) 1NT natural overcall does not occur so frequently - and when it does, many times you don't really want to play in 3NT (or even 1NT when partner is broke).

 

3) Losing the 1NT natural overcall hurts only in cases where your partner has most of the remaining points, which often (though not always) means that you'll be given enough room to explore the game.

 

I've been playing Raptor for a few years and I don't recall many cases where I'd miss a game because I could not overcall 1NT. On the other hand, I have already bid a few marginal games based on finding minor AND major fit early ;), I've already nailed a few good partscores easily, I've defended a few hands well with the knowledge from negative inferences etc...

[mikeh]

I am not entirely sure of the percentages, but my understanding has always been that 15-17 1N bids come along about 40% more often than 16-18, not 'definitely' more than 100% more often.

 

But even more importantly, most strong 1N overcallers, in my experience, use the range of 15-18 or 15+ -18, and so actually hold the hand more often than they hold a 15-17 1N opening bid, even allowing for the need for a stopper.

 

So your argument uses the 'straw man' approach: never very convincing.

 

Furthermore, an argument that states that the natural 1N is not good because you often do not want to play 1N or 3N is inane. Most partnerships have very comprehensive agreements over 1N, whether as an opening or an overcall, which allow for a wide range of contracts other than 1N or 3N :) Indeed, the reason that we have seen the explosion in the number of artificial defences to strong 1N opening bids is precisely because of the powerful nature of constructive methods available to the NT bidding-side. Raptor, on the other hand, is inherently difficult to move over in a constructive fashion because of the wide range in potential strength and the uncertainty as to the side major. I am NOT saying that it is impossible to move forward constructively, just that it is not as easy as it is to move over a strong 1N.

 

As for statements that are based on memory, the truth is that all bridge players (all humans) tend to remember triumphs for their world view (or pet convention) and tend to overlook costs, especially those that would not be immediately apparent. I do not doubt the sincerity of those who use this approach (I have fallen into this trap myself in the past and will probably do so again in the future), but I find such arguments to lack persuasive power. My suspicion is that few users of raptor give full weight to the cost imposed on other auctions, especially those that have to begin with double. Note that this extends to all immediate takeout doubles, not merely the ones with 15-17 balanced: your entire approach to takeout doubles must be distorted (whether you are conscious of it or not) if you must incorporate a natural 1N into your doubles.

 

That is not to say that raptor is a silly convention (such as mini-roman, as an example). I have played against raptor on a number of boards where the opps got good results, probably unattainable otherwise (they were not duplicated by my expert teammates). But I respectfully agree with everything Fred has written concerning its basic (relative) unsoundness.

 

Put another way: if I am playing against you and a raptor hand comes up, I will feel mildly inconvenienced if you are a raptor player, but on other, and probably more important hands, I will be much happier.

[han]

I felt the same way as Mikeh when reasing coyot's post, except for:

 

I am not entirely sure of the percentages, but my understanding has always been that 15-17 1N bids come along about 40% more often than 16-18, not 'definitely' more than 100% more often.

 

If the 40% you give is for opening bids, then the percentage for 1NT overcalls should be considerably higher (after all, RHO likely has a fair number of HCP). The exact percentage is hard to measure because it depends on their opening style.

 

Of course this is all moot because as you say

 

But even more importantly, most strong 1N overcallers, in my experience, use the range of 15-18 or 15+ -18

 

And in this forum we have seen that many good players are not afraid to upgrade their 14-count when they have good spots in the opponent's suit. But again, I think that you are wrong for the same reason as above when you say that:

 

and so actually hold the hand more often than they hold a 15-17 1N opening bid, even allowing for the need for a stopper.

 

When the opponents open at the 1-level then that significatnly reduces the odds that we will have 15-18 points. Or the other way around, when we do hold 15-17 points then it is fairly likely that the opponents do not have a good enough hand to open at the 1-level.

[inquiry]

I did a quick bridgebrowser check on the following condition.

 

1) a hand with 10 or more HCP opens 1c TO 1S.

2) NEXT HAND has 15-18 hcp and balanced pattern.

 

That is is... I looked at 300,000 auctions... the frequency was...this happened 1591 times out of the 300,044 hands I examined. Notice I did not look to see what the balanced hand bid.. just how often this occured.

 

This came to a frequency rate of about 1/2 of a percent, or one time out of every 200 deals. For math fanatics is this close to the right frequency you will be able to use 1NT given the constrains of an opening hand in front of you ( not considering psyches)

[han]

Ah, so we (partner plus us) should expect to overcall 1NT naturally in direct seat about once every 16 visits to the club. That is an extremely low number, thanks for the info Ben!

[Guest Jlall]

Ah, so we (partner plus us) should expect to overcall 1NT naturally in direct seat about once every 16 visits to the club. That is an extremely low number, thanks for the info Ben!

That seems wrong from experience. Then again I am prone to bidding NT :lol:

[pclayton]

It feels wrong to me too. 1 in 200? Thats once every 7 sessions - for the entire table. For our side thats 1 every 14 sessions. :lol: Thats once during a 7 day tournament.

 

I would think the frequency where we overcall a natural 1N is more like 1 per every 2 or 3 sessions.

[luke warm]

well unless ben made some sort of error (which i doubt), those are his findings.. *if* that's correct, does it matter to the 1nt bidders? if not, why not?

[inquiry]

well unless ben made some sort of error (which i doubt), those are his findings.. *if* that's correct, does it matter to the 1nt bidders? if not, why not?

Well even i find that number hard to believe. once every 200 deals is probably not right. I think I must have done something wrong. I will approach it a little differently.

 

Since pclayton says that he overcalls 1NT once every 2 to 3 sessions, so I choose to look at his hand using bridgebrowser and tournament/team games in the last quarter. He played 336 hands, and his side overcalled 1NT a total of 4 times (15 points once, 17 points twice, 18 points once). So that is 4 times out of 338 hands. Assume 26 boards per session that is a total of 13 sessions, so his rate is once every 3.2 sessions, sort of what he predicted (at 26 boards per session, that would be once ever 84 boards).

 

I agree this is more logical.. i will check to see what i did wrong the first time. An aside, 1NT overcalls were not all that successful for phil, but with only 4 boards, i think that is meanless...

[pclayton]

well unless ben made some sort of error (which i doubt), those are his findings.. *if* that's correct, does it matter to the 1nt bidders? if not, why not?

Well even i find that number hard to believe. once every 200 deals is probably not right. I think I must have done something wrong. I will approach it a little differently.

 

Since pclayton says that he overcalls 1NT once every 2 to 3 sessions, so I choose to look at his hand using bridgebrowser and tournament/team games in the last quarter. He played 336 hands, and his side overcalled 1NT a total of 4 times (15 points once, 17 points twice, 18 points once). So that is 4 times out of 338 hands. Assume 26 boards per session that is a total of 13 sessions, so his rate is once every 3.2 sessions, sort of what he predicted (at 26 boards per session, that would be once ever 84 boards).

 

I agree this is more logical.. i will check to see what i did wrong the first time. An aside, 1NT overcalls were not all that successful for phil, but with only 4 boards, i think that is meanless...

Well like Justin, I guess I'm a bit of a hand-hog. :P

[Finch]

For math fanatics is this close to the right frequency you will be able to use 1NT given the constrains of an opening hand in front of you ( not considering psyches)

Ignoring distribution constraints (we'll come to these in a moment),

 

15-17 with no info about the opposing hands = 10.1%

16-18 ditto = 7.3%

 

15-17 given that RHO has 11-19 = 2.5%

 

So you are about 4 times as likely to have srong NT values before they've opened.

As a slight side issue, my 1NT overcall range is also slightly larger than my opening range, and the distribution constraints are also less strict. But I insist on a stop in their suit, and some 1NT openers would be a take-out double (KQxx Kx Axxx KQx is a 1NT opening but a double of 1H).

 

So I would expect the ratio to be about the same.

 

I can put the distribution constraints in as well if you like, it'll take a bit longer and a simulation is probably faster....

[Sigi_BC84]

Well even i find that number hard to believe. once every 200 deals is probably not right. I think I must have done something wrong. I will approach it a little differently.

I have done a simulation, yielding the following:

 

(1x)-1NT: 0.010568

(1x): 0.339665

Generated 1000000 hands

Produced 1000000 hands

Initial random seed 1139575354

Time needed 2.813 sec

 

I've assumed a rule-of-20 opener that is not balanced 15-17 and weaker than 20 HCP. For the overcall I've ignored any stopper requirements and assumed a range of 15-18 HCP.

 

The figures say that the natural NT overcall occurs in about 1% of the boards (with 1st hand opening and 2nd hand overcalling). 1st hand opens in about 34% of the boards.

 

I may have made a mistake in my specifications, so if anyone cares, here is the dealer script I've used (without loss of generality I've chosen west to be dealer and hence north to be overcaller):

 

# 1 mio hands
generate 1000000

hw = hcp(west)
spw = spades(west)
hew = hearts(west)
diw = diamonds(west)
clw = clubs(west)

rule_20_opener = ( hw <= 19 and ( hw + spw + hew >= 20 or
       hw + spw + diw >= 20 or hw + spw + clw >= 20 or
       hw + hew + diw >= 20 or hw + hew + clw >= 20 or
       hw + diw + clw >= 20 ) )

balanced = shape(west, any 4333 + any 5332 + any 4432)
open_1nt = ( hw >= 15 and hw <= 17 and balanced )

first_seat_opens_1suit = rule_20_opener and not open_1nt

overcall_1nt = ( shape( north, any 4333 + any 5332 + any 4432 )
       and hcp(north) >= 15 and hcp(north) <= 18
       and first_seat_opens_1suit )

action average "(1x)-1NT" overcall_1nt,
       average "(1x)" first_seat_opens_1suit

[hrothgar]

For math fanatics is this close to the right frequency you will be able to  use 1NT given the constrains of an opening hand in front of you ( not considering psyches)

Ignoring distribution constraints (we'll come to these in a moment),

 

15-17 with no info about the opposing hands = 10.1%

16-18 ditto = 7.3%

 

15-17 given that RHO has 11-19 = 2.5%

 

So you are about 4 times as likely to have strong NT values before they've opened.

As a slight side issue, my 1NT overcall range is also slightly larger than my opening range, and the distribution constraints are also less strict. But I insist on a stop in their suit, and some 1NT openers would be a take-out double (KQxx Kx Axxx KQx is a 1NT opening but a double of 1H).

 

So I would expect the ratio to be about the same.

 

I can put the distribution constraints in as well if you like, it'll take a bit longer and a simulation is probably faster....

Are you sure about theconditional probability of 15-17 HCP?

 

I ran a very simple Monte Carlo simulation based on the assumption that South has 12+ HCP....

 

Here's a quick frequency distribution explaining how often East has "X" HCP

 

15 HCP = ~2.43%

16 HCP = ~1.54%

17 HCP = ~.9%

18 HCP = .5%

 

The percentage that South has 15-18 HCP looks substantially higher (~5.37)

 

I'm going to assume that South's shape is independent of North's decision to open or East holding 15-17 HCP. (Probably nort strickly accurate, but MUCH easier)

 

East will hold 4432/5332/4333 shape 47.61%

 

The probability that East has 15-18 HCP AND a balanced hand = 2.56%

[whereagles]

So, what's more frequent? Raptor or nat 1NT? :)

[inquiry]

So, what's more frequent? Raptor or nat 1NT? :)

There is no question raptor is more frequent assuming you use a wide hcp range. To run a simulation you would need to set some limits on the hcp range, of course.

[Finch]

Are you sure about theconditional probability of 15-17 HCP?

No, sorry, forgot to divide by P(11-19) in the first place.

It's actually about 5.9%, so a 1NT overcall in strength is a little more than half as likely as a 1NT opening.

 

If someone else has passed first the percentages of both go up.

 

I'm not taking out 15-17 in opener's hand when calculation the chance of 15-17 in overcaller's hand, because not everyone plays strong NT.