Free's 3NT lead hypothesis

[Free]

I also think this needs to be solved DD, not with BB... The data is flawed, but it may be useful for other purposes.

[inquiry]

I also think this needs to be solved DD, not with BB... The data is flawed, but it may be useful for other purposes.

Curious claim. I wonder why double dummy is fine, but bridgebrowser is "flawed". You do know that over thousands of hands, bridgebrowser data and double dummy data agrees. How often have you looked at real bridgebrowser data? Do you have a subscription? Do you have a DVD of data or a couple of CD's? Just wondering on what you make this claim.

 

The BRBR data is as good or as bad as you can define the hand selection data. If i select opening lead from a five card suit headed by AKQJT, I suspect I will get great results for that lead, but that is not very useful.

[hrothgar]

I also think this needs to be solved DD, not with BB...  The data is flawed, but it may be useful for other purposes.

Curious claim. I wonder why double dummy is fine, but bridgebrowser is "flawed".

I think that that Justin's post explained the problem with using Bridge Browser to study this type of issue.

 

If I use a Double Dummy solver to study this issue, my input will be an unbiased sample of N hands.

If I use BridgeBrowser, the initial sample will be biased.

 

Garbage In, Garbage Out

[sfbp]

99% of the bridge playing world lead 4th highest of their longest and strongest against the auction 1NT-3NT.

tch tch Frances, I can't leave that one untouched, an actual numerical claim with easily testable hypothesis :P

 

My measurements show it's in the 65-68% range. I checked the bbo main room, bbo tourneys, okbridge main room, okbridge tourneys, and this number is consistent to within 1 percent.

 

bbo main room is about 68%

bbo tourneys 65%

okbridge main room is about 68%

okbridge tourneys 66%

 

The only exception was the world championship data (very small data set) about 63%. Here it may well be that the data is woefully mucked up anyway, as the PBN files were rather disorganised, and frequently the full hand data was not available. So this one should be taken with a grain of salt. I never released this data set, there were far too many oddities and irregularities for it to be useful.

 

(added about 2 hours later)

I realised over supper that this 1/3 was a bit too high. Of course programmers make errors, I had been expecting somewhere in the 80's but not 99 and not 69, to be perfectly honest.

 

The problem was in a nutshell, there is more than one long suit in certain hand patterns - 4432 4441 5521 5530 and 6610 to be exact. And I'd saved the "longest suit" years ago without ever using the data, and without ever thinking about this problem.

 

Anyway it's fixed now, and 14% is a lot more than the 1% you postulated, Frances.

 

Sorry for any head scratching that may have gone on.

(end of edit)

 

I invite anyone to try it who has access to BRBR data.

 

Stephen

[Flame]

Can we comapare only hands where there was actually atleast one pair who lead from 4 cards and one pair who lead from 5 cards ? (if there are enough sample we can change this to more then one to avoid strange leads)

I think this way we might solve this problem and get a trustable result.

[inquiry]

Couple of issues. To flame's question, yes. If you click on the bar for leads from any suit legnth, you can call up all thos hands, create a board index with those board numbers, and then study just those boards using the full power of the bridgebrowser (spot cards, compare the lead of short on those hands to leads from the 5 card suit. Split by hcp, suit quality, etc. That call up a data set, click on one or more bars, and then re-analyze is the best way to use bridgebrowser.

 

To Frances, what stephen says is that mathematically, the data suggest the lead from a five card suit when also holding a four card suit is less than your 99%. Unfortuanately, the blanket look at a lead suffers from a few problems. Your five card suit maybe a five card suit promised by declarer. Your partner may have overcalled, opened or preempted in one of your short suits, etc. One has to control for all these "obvious reasons" to lead something other than the longest suit. A simple 1N-3N auction with 54 in the majors, see what the opening lead approaches solving the initial problem, but opens the door to quality of the suits in choosing which to lead.

 

Finally to Richard, I find the "garbage in, garbage out" potentially offensive, and I am sure Stephen pickett will find it offensive. I will assume by "garbage in" you mean if you are not careful in picking the criteria for choosing a fair hand set. IF I searched only for 4 card suits headed by KQJx and five card suit by xxxxx with RHO bidding that suit, I am sure the majority will lead the four card suit, and in the long run that will give the best results. So I will assume that is what you mean, picking the data set and how to probe it requires careful thought.. a point I tried to make in the very post in this thread.

[hrothgar]

>Finally to Richard, I find the "garbage in, garbage out" potentially offensive,

>and I am sure Stephen pickett will find it offensive.

 

Stephen's a programmer. I expect that he recognizes that this expression has been commonly used by programmers for decades.

 

>I will assume by "garbage in" you mean if you are not careful in picking the

>criteria for choosing a fair hand set. IF I searched only for 4 card suits headed

>by KQJx and five card suit by xxxxx with RHO bidding that suit, I am sure the

>majority will lead the four card suit, and in the long run that will give the best

>results. So I will assume that is what you mean, picking the data set and how

>to probe it requires careful thought.. a point I tried to make in the very post

>in this thread.

 

You were the one who rather peevishly asked why BridgeBrowser was a poor choice for this type of study. The precise quote was

 

>Curious claim. I wonder why double dummy is fine, but bridgebrowser is "flawed".

 

The answer should be rather obvious...

 

You always cite how wonderful BridgeBrowser's automation is. However, in this example you are going to be forced to perform manual inspections of all the hands that you're looking at. You haven't significantly advanced the state of the art from the techniques that Paul Marston used 15 years ago when he was studying this same problem.

 

In contrast, the combination of a random dealer program and double dummy solver permits you to start with an unbiased sample and to completely automate the process. In turn, you can inspect orders of magnitude more hands.

[sfbp]

Yes, I find your attitude offensive. Certainly not to be answered in its current truculent state.

 

I recall when you were one of the biggest advocates of this idea. I hope others who believe your grand plans for the future of bridge note how you seem to behave when you get tired of *their* idea. Caveat Fred!

[hrothgar]

Yes, I find your attitude offensive. Certainly not to be answered in its current truculent state.

 

I recall when you were one of the biggest advocates of this idea. I hope others who believe your grand plans for the future of bridge note how you seem to behave when you get tired of *their* idea. Caveat Fred!

Stephen, I have always maintained that Bridge Browser is a great product. I still do. There are any number of tasks where BridgeBrowser is incredibly valuable. For example:

 

I often like to examine my board results playing MOSCITO and calculate my average score and standard deviation for different opening bids. I normally find that the 1♦ and 1♥ openings score are net winners, my strong club openings don't score particulary well, my 2♦ is a big winner but has a high standard deviation and so on. Bridgebrowser is phenomenal for this type of analysis.

 

In a similar fashion, many people like to understand where their good scores come from. Are they great at bunny-bashing? Alternatively, do they play a slow steady style that picks up a small number of IMPs across the board. Once again, Bridgebrowser is great for this type of calculation.

 

However, the fact that BridgeBrowser is the best solution for some types of analysis does not mean that it is appropriate for all types of analysis. Suppose that I went and build the best lawnmower that the world has ever seen. This doesn't mean that I should mount it in my living room and use it as a ceiling fan. Furthermore, if I tried to market my lawnmower as a ceiling fan I'd expect to get called on it.

 

Bridgebase has some enormous limitations. The most significant of which is that your database doesn't contain any information regarding the partner's definition of different opening bids. If you see a 14 HCP NT opening, theres no way to understand if the partnership is playing a 12-14 HCP 1NT opening and this is a good maximum or, alternatively, whether the partnership is playing a 15-17 HCP NT and the player decided to upgrade a "stellar" 14 count. I have consistently maintained that this issue severely restricts the type of analysis that you can do with BridgeBrowser.

 

Personally, I think that BrBr (or some similar product) has a bright future. I'm not sure whether it is ever going to be a great money maker - I don't think that Bridge Software has produced many millionaires - however, I think that the ideas that you pioneered are going to make a very significant contribution to bridge.

 

Lets look forward a few years and assume that you're able to interface BrBr with whatever Full Disclosure has mutated into. In an ideal word, that 14HCP 1NT opening would be tagged with a unique identifier. In a similar fashion, all my Frelling style 2♦ openings would be tagged with their own unique identifier.

 

Once you have this type of feature in place, you increase the power of BrBr enormously. Case in point: Assume that I open 1NT. BrBr could automatically search for all examples of 1NT openings with the same tag, and create a summary statistic describing the range of the opening bid. Maybe there will be a little graph with a probability density function documented expect hand strength. Potentially, the opponents could even specify whether the PDF should be based on High Card Points, Zar points, or whatever.

[Echognome]

I just wanted to add that I'm not slighting bridge browser either. I think Ben's attempts to analyze the data quite interesting. I am only stating that for this problem I find double dummy analysis to be more accurate. It is not that I think double dummy analysis is perfect either. It is just that we know what we are getting with double dummy, whereas with empirical bridge data, we have one major problem; namely selection bias. If you can adjust or correct for that, then I will be behind the numbers all the way.

 

The main problem comes when the treatment (in this case leading from the 4 card suit in with a 5 card side suit) is correlated with another hidden variable (here I believe it's suit quality OR it's the unknown auction OR it's major versus minor OR it may be MPs vs IMPs). In the case of the 5 card major in 1NT (which I thought was an excellent idea to consider) the hidden factor was that expert players are more likely to open 1NT with a 5 card major than beginners. I appreciate on this example you controlled for IMPs versus MPs. You can also control the auction by considering auctions such as 1NT-3NT. It seems you can also control for suit quality if you spent a little time. Then you just need to control for major or minor, as auctions such as 1N-3N typically mean that responder does not have a 4 card major, and most definitely not a 5 card major.

 

I think the main point is that if brbr is to be useful for answering more general questions (and I have no doubt it is useful in looking at your own system), then the studies themselves have to be done carefully and controlling for as many factors as you can.

 

As per Richard's suggestion, I think that being able to filter (or as Richard used 'tag') our data based on what system we are playing would be a big plus. (Enough so that I would purchase the software outright.) But of course that would take some integration with bbo software. Say that we could keep track of how we did within one system. Perhaps there is a way around that by being able to look only at systemic bids, e.g. 1♦ opening with 9-15 hcp and 4+ hearts, but even then we may pick up some hands that have diamonds where we were playing a natural system all along. I don't know if this is possible or not, but it would make it easier if we could just select our system ahead of time and then all hands we played using that system are marked as such. I believe the easiest solution would be when we load an FD file, it sent a tag and the name of the FD file was stored on the database it would be sufficient. I also believe that those that play more artificial systems are more likely to want to use bridge browser as a tool. However, they are also much fewer in number! So, I can understand if you are not so concerned about catering to their needs.

[inquiry]

You always cite how wonderful BridgeBrowser's automation is.  However, in this example you are going to be forced to perform manual inspections of all the hands that you're looking at.  You haven't significantly advanced the state of the art from the techniques that Paul Marston used 15 years ago when he was studying this same problem.

Quite to contrary, you can automate essentially all the steps... if you are willing to frame the question appropriately. Let's take Flame's question as a jumping off point...

 

Here is a logical sequence of test, that apply very little initial selection criteria to see how things might progress... you can apply a hell of a lot more criteria if you would like. We will start with a simple search where leader against 3NT has any number of hcp but specifically 5431 distribution, and is allowed to lead any card. Let;s see how this is done..

 

From the contract menu, pick specific 3NT (the only green box in the list of contracts), i also excluded doubled and redoubled contracts, and today, I choose present data from the defenders point of view (see black box in the upper window below). I choose a single distribution for leader (5431), I could have choosen any two, three, four, up to all possible distibutions if I wanted, for instance, I cuold have choosen 5431 and 9112 for leader. I choose leader to have from 0 to 37 hcp, I could have choose 0 to 2 or 4 to 9 etc. See the green rectangles in the middle of the upper window.

 

I then searched a BBO database and stopped it when about 1/4 finished with the search. Since this was main room, it is not surprizing there was very few matchpoint hands, but I wanted them to illustrate a later point. But the results of the discovered 25044 hands where leader had 5431 on lead against 3NT, the results for the DEFENDERS this time are plotted in the lower window on the left hand side of the image.

 

But lets look at the top window for a minute. Each row is one hand where someone lead against 3NT. The hand correspondng to the highlighted hand is displayed on the lower right hands side.. I erased a little data that is hiddend by the yellow box in the hand diagram related to players rating. If you look at the one line, you can compare it with the actual hand. All the contracts were 3NT, we forced that, since we searched by defender on lead, the column headed by HP will list that defenders hcp, on the displayed hand, it says he held 7 hcp (green square) and the line points to him, showing he did have 7hcp. The declarers combined hcp is listed in the column headed HPT, it says they had 26, and if you run down the red line to look, they do (15 opposite 11), the last competitive bid other than pass (with respect to declarer;s side) is listed as 2H (colum headed (Cmp), and if you look, one defender did bid 2H (red line connects them). Note Pas(s) only shows up in this column if the "defenders" never bid. The vul (column Vi) is them (since we searched by defender), and the opening lead was the king of hearts (connected from top window to bottom by blue line).

 

http://1.forumer.com/uploads/homebaseclub/post-25-1160666042.jpg

 

For completeness there is a few more columns, Trt is trumps for the declaring side and DT is defender's turmps. In NT of course, these are zero. DT and DO are distributional points for declaring and defending side, and once again, by convention, these are considered 0 if in NT.

 

Now 25,000 hands is too many to much around with unless you have already applied all the criteria you were going to apply. Here we applied basically none. There is a lot of things you can do with this data on the screen, for instance, you can sort by any column header (player, lead, total declarer points, opneing leaders hcp (in this case), or competitive bid. For example, you easily pick only hands where the defending side didn't bid by sorting by the Cmp column and using your mouse to highlight and then display just the ones with pass (click first, then shift click the last in the listing).

 

But lets proceed with Flames question, cna you look at just the hands where people lead from one of the short suits. The answer to that is yes, easily. On the bottom left hand chart (the lead chart), just click on the bar for imp results when leading from a three card suit. When you do that, you will get only the hands that lead from a three card suit (in this case 1731 hands) http://1.forumer.com/uploads/homebaseclub/post-25-1160666019.jpg

 

When you plot the leads, you find, not surprisingly, that there were 1731 leads, and all were from 3 card suit, Note the matchpoint hands are gone, because I just clicked on the imp bar. This isn't so much useful at first glance but there is a lot of things you can do with this data. For one thing, you can create a board file, so that future inquiries will be restricted to only these deals (thus, any lead from a five card suit or 4 card suit will be from the same hand a lead from a 3 card suit occured). You can push these hands over into bid analysis and open up the full power of investigating by sequence, suit quality, tricks taken, etc, as I do in this example For instance, lets look at the lower left hand window in the diagram above. First, we should see that the total number deals in 1731 there too... (the little box a few inchies to the left above the blue highlighted tab that says bid analysis, Second, if we look at the table in that same window, we see alisting of opening bids, starting with pass, with 1NT the last opening bid readable, but you can also see part of 2C. The number to immediate right of those bids indicate opening bid by the patnership that willl eventually defend on this hand (since we searched origianlly by defender). So you see that the hand was opened by the defenders in 1H and 1S a total of 458 times. By clicking on those two bars, an dyou can run analysis on how well third best lead works after your side has opened in a major. The next graphic gives that information in two formats...

 

http://1.forumer.com/uploads/homebaseclub/post-25-1160666000.jpg

 

Above we see when we grab just the hands that open 1M and they play 3NT (again our leader has to be 5431), you can see there was the 458 hands (in a number of places you can see that number). In addition, the results show that after opening 1H the average result in imps for leading from a three card suit was -0.38 imps (top row in the red box in the column headed AvIMP), and for a spade lead a more profitable 0.16 imps. Since we plotted a 3 card lead after opening either 1H or 1S, we see that leading a three card, we see the average result was -0.16 (not surprising, multiple 222 by -.38 and 236 by .16, sum the results and divide by the number of hands (458).

 

Of course a lot of other factors might go into the figure the result. One such factor might be quailty of the suit. Let's take a look at the quality of the 1S suit opened versus the result...To get the following chart, simply click on the 238 next to 1S and choose plot, then from the options (tricks, hcp, contract, suit, etc...) pick suit.

 

http://1.forumer.com/uploads/homebaseclub/post-25-1160668588.jpg

 

This chart shows the quality fo the 1S openers suit. I then clicked on the bars that included at least two of the top five honors ,,, but had to include Ace or King. There were 132 such hands, and the average result for the defenders when the suit had 2+ honors including the A or K was a pllus 0.41 imps.

 

So I will go back and restate the obvious. It is up to the person using BRIDGEBROWSER to frame the question being asked appropriately. Worried about justin's concern that an honror lead from a sequence in a short suit might take precedence over low card from longer suit? Then on the contract page, choose a lead where the card can not be higher than an 8 for instance (see the green box on the top window in the middle). Worried that partners bid might affect the lead, only look for leads where partner has not bid. Create several search results and build board files then probe deeper using just those hands. Wondering rather leading a short suit when weak is better than leading your long suit opposite a passing partner? Restrict leaders hcp and force partner to pass, and compare with similar leads when you have more hcp. A blanket which lead is best with no other application to control for significant variables, is of course, "garbage in", but you can fine tune your requrirements of litterally tens or hundreds of million plays... and should be able to get useful data... For instance, I think I demonstrated that people tend to open 1S with 5-1-6-2 when weak and 1D when stronger in antother thread using bridgebrowser. That was obvious, but we could put some number on the frequency.

[inquiry]

BTW. you can do esoteric things as well. For example, for those of you who think the average player on BBO or OKB is too weak, and so will lead randomly, you can do this...

 

1) go to player tab, enter minimum rating for opponents (say 55 == which is low level expert, high level advanced, or 60 which is expert, or 65 which is world class).

2) do contract search as played by declarer. This will restrict the oopening leader to having a rating of at least that high (54.5 rounds up to 55, etc).

3. Then build a board index using those hands, and then choose 3NT defend, with the rating index again at the same level. This will give you just the hands where declarer and leader have whatever minimum range you want. At the very least you can check to see why such players choose an odd lead like a singleton (partner bid suit most likely cause), or 3 card suit lead.

 

The screen looks like this...where I set the minimum rating to 55....

http://1.forumer.com/uploads/homebaseclub/post-25-1160673869.jpg

 

BTW, this is the search screen most players use, and they never get past the entering their own name (or fulvio2002 or fred) in the player field. You can provide virtually unlimited seach criteria (like adding minimum lehman like rating to the results found), suit quality, opening bid(s), vul, range of cards lead, hcp ranges, etc.. and you can then take the found data and prune it and subdivide it even further.

[Cascade]

I also think this needs to be solved DD, not with BB... The data is flawed, but it may be useful for other purposes.

There is another solution we can use single dummy results.

 

Somewhere I have over 100000 hands played by GIB on the auction 1NT 3NT. On each hand I forced the opening leader to lead from each suit - GIB didn't mind playing the hands four times.

 

I think from memory I restricted the opening leader to hands with no voids and no six-card or longer suits.

 

I will try and post some of the results later but I have a busy day and I am away tomorrow so it might not be before the end of the weekend.

 

Single Dummy is much slower than Double Dummy so is not so popular but does not suffer from some of the objections of DD and BB studies.

[barmar]

One problem with trying to use DD analysis for this is that the DD solver cheats when deciding the opening lead, so that will presumably bias the results. It always chooses the "right" lead. This is kind of related to Justin's point about leading from his 4-card suit when there's something about the suit that makes it inherently more attractive than the 5-card suit.

 

What I think you need to do if you're going to test this hypothesis is force a particular lead, then perform DD analsys starting from trick 2 (or from declarer's play of the dummy on trick 1). For every hand in the collection, first have opening leader lead from his 5-card suit, then start again and have him lead from his 4-card suit, then compare the results.

[Al_U_Card]

If I follow, we have indicated that DD analysis gives about the same result as actual play.....

 

Is not DD analysis, the "perfect" solution and play is the real-world approximation?

[cherdano]

I also think this needs to be solved DD, not with BB...  The data is flawed, but it may be useful for other purposes.

There is another solution we can use single dummy results.

 

Somewhere I have over 100000 hands played by GIB on the auction 1NT 3NT. On each hand I forced the opening leader to lead from each suit - GIB didn't mind playing the hands four times.

 

I think from memory I restricted the opening leader to hands with no voids and no six-card or longer suits.

 

I will try and post some of the results later but I have a busy day and I am away tomorrow so it might not be before the end of the weekend.

 

Single Dummy is much slower than Double Dummy so is not so popular but does not suffer from some of the objections of DD and BB studies.

I agree this will be a very useful analysis, but it still has bias. How often will GIB as opening leader's partner stubbornly lead back the original suit, assuming this will be opening leader's best suit?

 

Arend

[joshs]

How about comparing leads when the two suits are:

HMSSS vs HMSS

Where:

H is one of AKQ

M is one of JT9

S is anything smaller.

 

Thus here we would be comparing 5-4 hands where the two suits have roughly similar suit quality and means that neither suits has a 3 card honor sequence.

 

Additionally, subdivide the cases into:

a. Both suits are majors

b. both suits are minors

c. 5 card suit is a major, 4 card suit is a minor

d. 5 card suit is a minor, 4 card suit is a major

 

This should account for most of the reasons why people would normally lead a 4 rather than a 5.

 

Note: There are still additional issues. One of the gains of leading a 4 instead of a 5, is that declarer will miscount the hand, and misguess a side suit. This advantages goes away once you are known to favor leads from the 4 card suit. This is similar to the advantage you might get from using a convention/treatment but not giving full disclosure.

[inquiry]

btw can everyone see these graphic inserts ok.. I have these huge monitors with crazy resolution and I had this horrible thought that they are much too big for average to small size monitors....

[inquiry]

How about comparing leads when the two suits are:

HMSSS vs HMSS

Where:

H is one of AKQ

M is one of JT9

S is anything smaller.

 

Thus here we would be comparing 5-4 hands where the two suits have roughly similar suit quality and means that neither suits has a 3 card honor sequence.

 

Additionally, subdivide the cases into:

a. Both suits are majors

b. both suits are minors

c. 5 card suit is a major, 4 card suit is a minor

d. 5 card suit is a minor, 4 card suit is a major

 

This should account for most of the reasons why people would normally lead a 5 rather than a 4.

 

Note: There are still additional issues. One of the gains of leading a 4 instead of a 5, is that declarer will miscount the hand, and misguess a side suit. This advantages goes away once you are known to favor leads from the 4 card suit. This is similar to the advantage you might get from using a convention/treatment but not giving full disclosure.

You have hit upon one weakness in Bridgebroser. The data is indexed, so it can be searched quickly, each item indexed (vul, hcp, distirubtion points, suits headed by just Ace, by just king, by Ak, etc) increases the data size and the search time tremendously. As I understand it, one trade off was to index by jus the follwoing suits...

 

xxxxxxx

Jxxxxxx

Qxxxxx

Kxxxxx

Axxxxx

QJxxxx

KJxxxx

AJxxxxx

KQxxxxx

AQxxxxx

AKxxxx

KQJxxxx

AQJxxxx

AKQxxxx

AKQJxxx

 

(and these honor combianations at all the various suit legnths). Thus, Tens and Nines are not searchable, and treated as "x"'s. I commented on this to stephen in the past, and in this thread already. funny, nowever you can search for leads by T's or 9's... from the contract page, which really works... and you can combine that with higher honors using selection criteria, but if they don't lead it, you don't see it....

 

You can look for AKQJT or 9 leads from either suit as part of the requirement... you can do some combined searches.. search for one setting, save as board file, search with some more criteria -- and add to the board file, then analyze the board file with only hands that match one (or more) of your different search criteria.

[awm]

There are a number of things you might want to measure in bridge. Basically, BridgeBrowser is a good tool for measuring "what do people do on real hands." It's very clear that if you want to ask something like: "how often do people open in third seat with less than 12 hcp" bridgebrowser will give you a perfect answer based on real data.

 

On the other hand, if you want to ask a question like "what is the best play," bridgebrowser is somewhat less useful. The reason is, anything you try to measure will be biased by the "what people do." For example, let's take opening leads.

 

We'd like advice about how to lead against the auction 1NT-3NT (say). Obviously what I'd like to do is to always make the double-dummy ideal lead. If several leads are double-dummy equivalent, I'd like to make the one that maximizes declarer's chances to go wrong (i.e. don't solve a two-way guess via the lead). I think it's fairly straightforward that this is the meaning of making the best lead.

 

Looking at that, it's immediate that what I need to do is produce hands where the auction goes 1NT-3NT and then do a double-dummy analysis. This would be a combination of BridgeBrowser (to find 1NT-3NT auctions) and deep finesse or GIB. I can't easily use JUST DF or GIB because those tools can't tell me when people will bid 1NT-3NT. I could of course enter my own criterion for 1NT-3NT, but different people open/raise in different ways.

 

How come I can't just use BridgeBrowser alone? The issue is that people's leads are biased by "who they are." Suppose that everyone used a lead algorithm of:

 

(1) If I have a 3+ card honor sequence, I always lead from that sequence.

(2) If I don't have such a sequence, I lead 4th from longest suit.

 

Under these criteria, all the leads from four card suits on 5431 patterns will involve honor sequences. I'd expect that these leads look "really good." So BridgeBrowser will tell me that the four card leads are great! But that's not really helping when I don't have the honor sequence, is it?

 

Of course, I could control for this by restricting suit quality. Now if everyone leads as above, we'll see everyone leading the same card and BB won't help at all. But suppose that the algorithm above is used by almost all beginners/intermediates, but that experts have a more complex approach. Then we'll see that all the leads from four-card suits where there's no honor sequence happen to be by expert players. Expert players tend to get better results than beginners. So again the leads from four card suits look great!

 

So now I need to control for the suit quality, and the player level, and probably the level of opponent as well. Suppose that once you do all this, it's right to lead from the five card suit 90% of the time. We'd really like the answer in this case to be "lead from the five card suit is best." But suppose the expert players actually already tend to lead from the five-card suit even more than 90% of the time. And the few four-card suit leads they make are generally right. It'll still appear that the four-card suit lead is "better" because when the experts do it, it's usually right.

 

To try and make this clearer, my personal lead style is to almost never underlead kings against suit contracts. I believe that underleading a king (especially against a freely bid game) is much more likely to give a trick than accomplish anything. With this said, some auctions simply scream for an active lead. In those cases I will underlead a king. So if you analyze my results on opening leads, you'll find that the times I underlead a king against a suit contract I almost invariably made a good lead, whereas the times I didn't underlead a king it's more of a tossup. You could use this to conclude that "underleading kings is good" when that's exactly the exact opposite of my opening lead philosophy! So you have to be careful with these sorts of statistics...

 

In any case, what all this BB analysis of opening leads will tell us, is whether players on BBO (or OKB) tend to lead too often from the five card suit, too often from the four card suit, or about right. If you restrict by player skill level you can answer the same question about "expert" players. But it won't tell me what is the best lead.

[joshs]

Adam raised many ofthe issues we have discussed before, as limitations of doing certain types of statistical analysis with bridgebrowser.

 

For instance if I wanted to know if my weak 2's should promise 6 cards and 2 of the top 3 honors, the questions I need to answer are:

 

a. How many imps or mps do I win when I open a weak 2 that promised 2 of the top 3 honors compared with players who opened the same hand with a looser definition?

b. How many imps or mps do I win (or lose) when I pass a hand that looser players open a weak 2.

c. Then combine these based on the relative frequencies of the two hand types.

 

The results from a and b have nothing what so ever to do with the results from:

d. How many imps or mps do I win/lose when I open a weak 2 with 2/3 honors

e. How many imps or mps do I win/lose when I pass a potential weak 2 that doesn't have 2 of 3 honors

 

Also, there is the repeated question of a biased sample. For istance, if canape leads scored better than 5 card leads when it was an auction chosen at few tables, thats a better argument for them than if they performed better when they were chosen at many tables (usually an honor sequence). Anyway, its very difficult to do a good statistical hypothesis test to answer the questions we are raising using the data thats in bridge browser....

[inquiry]

a. How many imps or mps do I win when I open a weak 2 that promised 2 of the top 3 honors compared with players who opened the same hand with a looser definition?

b. How many imps or mps do I win (or lose) when I pass a hand that looser players open a weak 2.

c. Then combine these based on the relative frequencies of the two hand types.

 

The results from a and b have nothing what so ever to do with the results from:

d. How many imps or mps do I win/lose when I open a weak 2 with 2/3 honors

e. How many imps or mps do I win/lose when I pass a potential weak 2 that doesn't have 2 of 3 honors

 

Also, there is the repeated question of a biased sample. For istance, if canape leads scored better than 5 card leads when it was an auction chosen at few tables, thats a better argument for them than if they performed better when they were chosen at many tables (usually an honor sequence). Anyway, its very difficult to do a good statistical hypothesis test to answer the questions we are raising using the data thats in bridge browser....

Well of course, bridgebrowser does not analyze partnership agreements, so you can not ask these types of questions. Richard points this out in his comments as well, as there is no way to apply negative/positive impications to the bid.

 

You can, if you want, ask other questions, how well does opening 2H on a five card suit do on average. This doesn't address whether there is a partnership agreement to do so, and added to the mix, even if you restrict the hand to "weak" the opening bid might be lucas or something, shoiwing five and another four card suit. So there is a lot of difficulty. Studying bids that start 1C and 16+ hcp will not tell you how precision works, because Standard players open 1C with 16+ all the time wihen 1C is the right opening bid. I dont think anyone has tried to build a bidding system using bridgebrowser data, or to support building one (an exception in a moment). This is richards complaint because he wants to study the impilcation of defined bids, which of course you don't have. You have a bid.. and a specifc time.

 

Of course, you could pick nunes and fulvio202 and use bridgebrowser to look at all the hands they have played on line at bbo (and if you know their nicks at okbridge). Then use bid analysis to subdivide each acution, then use plot to see the frequeny of hcp, distributions, and the like they have for every bid. So you could study systems that way, if the pair has enough hands. Or you can use bridgebrowser to find certain hand types, say a weak two on a five card suit, or discipline weak twos by how ever you define them, and then see how your system would have handled them. I used bridgebrowser to find 20,000 unique misiry hand types to use to build my misiry convention. That was too many, as I will not work much beyond a few thousand...

 

So study other players, get example hands to try yoru system on (download to pbn and use in partnership bidding), replay yoru hands dobule dummy, replay someone else hands where you can only see their hand, and prss the "next key" button, then see if the card you would have choosen is the card they would... great tool.... those replays are in pllayed on netbridgevu loaded from bridgebrowser and you click the hand of the player you want to play from , and decide on your card before you press "next" card button. Then there is also the option to replay the hands loaded from bridgebrowser in netbridgevu as double dummy, where you can pick the card to play (you have to be looking at all four hands to do that).

 

The for the maniacs, you can try the statistical stuff... the worse contact in bridge? I know you are thinknig 2NT.. but you would be wrong. The worse is 5NT, and it is not even particularily close. But then, brige logic would probably have told you that even if I hadn't found it out using bridgebrowser.

[joshs]

a. How many imps or mps do I win when I open a weak 2 that promised 2 of the top 3 honors compared with players who opened the same hand with a looser definition?

b. How many imps or mps do I win (or lose) when I pass a hand that looser players open a weak 2.

c. Then combine these based on the relative frequencies of the two hand types.

 

The results from a and b have nothing what so ever to do with the results from:

d. How many imps or mps do I win/lose when I open a weak 2 with 2/3 honors

e. How many imps or mps do I win/lose when I pass a potential weak 2 that doesn't have 2 of 3 honors

 

Also, there is the repeated question of a biased sample. For istance, if canape leads scored better than 5 card leads when it was an auction chosen at few tables, thats a better argument for them than if they performed better when they were chosen at many tables (usually an honor sequence). Anyway, its very difficult to do a good statistical hypothesis test to answer the questions we are raising using the data thats in bridge browser....

Well of course, bridgebrowser does not analyze partnership agreements, so you can not ask these types of questions. Richard points this out in his comments as well, as there is no way to apply negative/positive impications to the bid.

 

You can, if you want, ask other questions, how well does opening 2H on a five card suit do on average. This doesn't address whether there is a partnership agreement to do so, and added to the mix, even if you restrict the hand to "weak" the opening bid might be lucas or something, shoiwing five and another four card suit. So there is a lot of difficulty. Studying bids that start 1C and 16+ hcp will not tell you how precision works, because Standard players open 1C with 16+ all the time wihen 1C is the right opening bid. I dont think anyone has tried to build a bidding system using bridgebrowser data, or to support building one (an exception in a moment). This is richards complaint because he wants to study the impilcation of defined bids, which of course you don't have. You have a bid.. and a specifc time.

 

Of course, you could pick nunes and fulvio202 and use bridgebrowser to look at all the hands they have played on line at bbo (and if you know their nicks at okbridge). Then use bid analysis to subdivide each acution, then use plot to see the frequeny of hcp, distributions, and the like they have for every bid. So you could study systems that way, if the pair has enough hands. Or you can use bridgebrowser to find certain hand types, say a weak two on a five card suit, or discipline weak twos by how ever you define them, and then see how your system would have handled them. I used bridgebrowser to find 20,000 unique misiry hand types to use to build my misiry convention. That was too many, as I will not work much beyond a few thousand...

 

So study other players, get example hands to try yoru system on (download to pbn and use in partnership bidding), replay yoru hands dobule dummy, replay someone else hands where you can only see their hand, and prss the "next key" button, then see if the card you would have choosen is the card they would... great tool.... those replays are in pllayed on netbridgevu loaded from bridgebrowser and you click the hand of the player you want to play from , and decide on your card before you press "next" card button. Then there is also the option to replay the hands loaded from bridgebrowser in netbridgevu as double dummy, where you can pick the card to play (you have to be looking at all four hands to do that).

 

The for the maniacs, you can try the statistical stuff... the worse contact in bridge? I know you are thinknig 2NT.. but you would be wrong. The worse is 5NT, and it is not even particularily close. But then, brige logic would probably have told you that even if I hadn't found it out using bridgebrowser.

Thats a funny observation. I average playing in 5N about 3-4 times a year, and win about 8 imps/bd on those hands (I am estimating since I haven't written down all my results anywhere). I think I have a statistical sample of 20 boards in real live bridge which isn't a huge sample. but its enough to know this isn't a fluke (I have played that contract much more since I started playing relay. It probably was only a once a year contract before that)...

 

They tend to fall into two categories, on most of them the contract was 6 something at the other table, usually going down with 5N making, and occasionally the contract is 3 or 4N or 5m with 5N making for a push. I actually don't ever remember playing in 5N and going down. But I guess in the rank and file, when they play 5N its either because:

a. one of the players doesn't know what the bid means, and passed for a major accident

or

b. someone had already made a major overbid prior to them getting to 5N

 

Probably most a, someone passed "Choice of Slams".

For instance, I expect the auction (opps silent):

1N-5N-P

or

1N-2D-2H-5N-P

To score terribly since 5N was forcing in both auctions....

[inquiry]

Probably most a, someone passed "Choice of Slams".

For instance, I expect the auction (opps silent):

1N-5N-P

or

1N-2D-2H-5N-P

To score terribly since 5N was forcing in both auctions....

Well we can quickly dismiss these two auctions as a major cause to the bad results on average for 5NT. Lets look at the data for the most recent BBO tournament/team game database....

 

Here is the data... this is ALL the 5NT contracts. The first chart to look at is this one.. let's get orientated to the way this display works... On the left hand side is "bids" so 5NT is the bid that we are interested in. Note the columns have headers, ----

Bid open Interv Resp Adva Rebid other CtrOs CtrNOs AvIMP #Imp AvMP #MP

 

Well, bid is the bid, open means opening bid. One person opened 5NT. Intervention means person behind opener bids, so one person overcalled 5NT (and played it there), REsponse if the first bid in response to opener. So 14 people responded 5NT to the opening bid, the next bid is advancer, so after an overcall, 6 advancers jumped to 5NT, the next (rebid) is openers rebid, 60 people rebid 5NT, the next is the second rebid by overcaller, or rebid by responder or advancer.

 

So let;s test your first two hypotheses, first the bidding when 1x-5NT and opener mistakenly passed, or the auction went 1x-2y-2/3z-5NT and responder passed.

 

http://1.forumer.com/uploads/homebaseclub/post-25-1160696188.jpg

 

We find that only 14 out of 2465 auctions went 1x-5NT-pass. That is 0.5%, we can safely ignore that for the reason why 5NT is a bad contract. But while we are here, how bad did 1x-5NT do? We find this by using the slider. I have put a red square around the slider, and slide it over the "Resp" column. When you do this the last four columns show the results for these "14" hands. First, we see that 12 of the 14 5NT responses occured at imps (the 12 in the #imps) coumn, and these averaged a minus 3.91 imps. The two matchpoint hands, however were very good (85.22%).

 

Now lets look at auctions that went 1x-something-something-5NT rebid by responder as his second bid. There were 180 of these, which accounts for 7.3% of the auctions, taken together the auction you mentioned that account for the "bad results" of 5nt contract was less than 8% of all such auctions. When we move the slider over, we see that average result for responders rebid of 5NT (and playing 5NT) was -3.39 imps (115 auctions) and 36.67 (65 hands).

 

http://1.forumer.com/uploads/homebaseclub/post-25-1160696171.jpg

 

So could these 8% of all 5NT bids account for the poor result of 5NT? Lets see. We can slide the slider over CtrOS (contract opener side---upper chart below) or over CtrNOS (contract non-opener side ---lower chart) and see how the 5NT averages..

 

http://1.forumer.com/uploads/homebaseclub/post-25-1160696211.jpg

 

http://1.forumer.com/uploads/homebaseclub/post-25-1160696259.jpg

 

Well, as we can see, the average result for 5NT by either openign side or responder side were both WORSE than the average result for the two auctions you speculated caused the poor result. If it is not your view that people totally don't know how to bid, what could it be? By right clicking on one of the numbers (in this case the 2268 in the CtrOS you can plot the data, in lots of ways. Below is a plot of tricks won when 5NT was played by the opening side. I further clicked on just the column that took 11 tricks. The results of that click (the numbers below the chart) show that of the 2268 hands, 621 hands made exactly 11 tricks. When exactly 11 tricks were made, the average result was a nice +2.26 imps or 64.25% matchpoints. Slightly better than what the average 3NT making averages and no where near you +8 imps you are so lucky to make in your average 5NT contract.

 

The problem is 5NT is making on the nose only 25% of the time. When 5NT goes down, (click on all the bars with less than 11 tricks, and the software will show you the number of hands and averages for those, the result is a pitiful -9.03 imps and a frightening 11.87% at matchpoints. And when it makes one or two overtricks, the averages are -2.57 imps and only 44.28% matchpoints.

http://1.forumer.com/uploads/homebaseclub/post-25-1160696390.jpg

 

So i wonder what this data shows? So 25% a fair result, 75% of the time a bad result. It seems to show to me that playing 5NT carries the risk of going down when 3NT or 4NT was making, thus losing game bonus and giving opponents points to boot. Thus when you make you break roughly equal to those in game at a lower level, and when you go down, you lose big to them. It also has some mild risk you stopped one level too low, when the slam is making. You think 5H/5S is no mans land, overbidding game by one level, but not reaching slam, 5NT overbid the game level by two, but still gains ZERO bonus when it makes on the nose. That is all risk, no benefit. When stopping in 5NT is "good" is when you exited a slam auction that is going down, and then it is no better than 3NT for scoring purposes.

[hotShot]

If we want to investigate Free's 3NT lead hypothesis, we have to define precisely what we are looking for.

 

1) Obviously opps play 3NT.

2) The player who has the opening lead holds a 54xy distribution.

3) both suits are almost equal (honor strength) or the short suit is better

 

His only bidding example is (his side silent):

1♠ - 2♣

2NT - 3NT

 

Does this mean, it is a restriction, that his side is silent and if so, what is his partnerships agreement for overcalls with 5-4 distributions.

His example implies that opps don't need to open NT.

 

In this example opener is also declarer, is this a restriction too?

The hand given to this example is:

[hv=s=sqxhkxxxxdkxxxcxx]133|100|[/hv]

 

Both of his suits are unbid suits, is this a restriction too?

 

After reading the article my impression is, additional restrictions are:

 

4) Defending side had been silent.

5) Both of leaders suits are unbid.

 

Restriction 4 is the main problem when defining the search, because it depends on the overcall structure.

 

So it would be best to select deals from bridgebrowser that follows this restrictions.

 

1) Opener is declarer

2) The final contract is 3NT.

3) Defendig side has been silent.*

4) 2nd seat has 5-4 distribution with unbid suits.

5) Honor quality of the 4 card suit is better or about equal to the 5 card suit.

 

*Since overcall structures can be very complex this can mean a lot of different restrictions. I think it is possible to simplify by looking at opening bids 1♠ and 1NT to eliminate noise of lunatic 1-level overcalls. But to be accurate one would have to investigate all 1(something)- ...... - 3NT sequences seperately.

 

Since we need bidding information to select the deals, a simple double dummy solver won't help us much. But is bridgebrowser capable to apply these restrictions?

 

If so, we can look at the result set and compare the success, depending on the lead suit, if there are enough samples for both 4 and 5 card leads, we might see a significant result.