Bridge Hands on Bridgebase.

[IowaST8]

OK, Are the Bridge Hands on Bridgebase truly random? Or, are the hands sometimes padded to make the game more interesting?

[Gerardo]

Some tourneys have prepared (as in uploaded) hands. Randomness of those depends on the tourney organizer.

Players are informed when this happens, with a message "This tourney uses prepared hands" or something like that (sorry, didn't see the message in english in a while)

 

Instant Tournaments use hands recycled from old tourneys, but those were random the first time around.

 

Best Hand tournaments: South gets the hand with more HCP (or one of them if tied). Either by swapping or rotating, I don't remember.

 

No other hand is manipulated in any way.

 

Dealer's randomness has been tested for bias. No bias, truly random.

[pescetom]

If the hands look padded to you it may be because you have frequently played hands that were manually shuffled. Manual shuffling tends to produce less interesting hands than a genuine random shuffle.

[AL78]

It should be noted that streakiness is a property of randomness. I have streaks of getting poor hands and lower than average declarer play frequency, but when I have tested a sample distribution of the mean HCP I get dealt over several months, it comes out very close to the 10 HCP you would expect. If you ask someone to roll a dice and someone else to write down a sequence of random numbers from 1 to 6, it is possible to tell which sequence has come from rolling the dice, because what people think a random sequence should look like is different to how most random sequences really behave.

[thepossum]

I am wondering how you could test a single tourney's hands for randomness :)

 

But depending on how you look at randomness I think its quite obvious that sometimes the hands on BBO are random and sometimes not

 

I have definitely observed patterns in the hands from time to time :)

 

Also I am sure on occasion hands are dealt and balanced in someway across tournaments using a dealer script. So clearly not random at all

 

And who knows what shuffling algorithm they use

 

I have no idea how BBO deals their stuff :)

[smerriman]

But depending on how you look at randomness I think its quite obvious that sometimes the hands on BBO are random and sometimes not

 

I have definitely observed patterns in the hands from time to time :)

 

Also I am sure on occasion hands are dealt and balanced in someway across tournaments using a dealer script. So clearly not random at all

You seem to be fundamentally misunderstanding what 'randomness' means. If you *couldn't* spot patterns from time to time, that would prove beyond doubt that the hands were *not* random.

 

Unless you're referring to some Goulash-style tournaments, which are specifically handcrafted and thus not relevant to this discussion, it has been shown time and time again there is no bias in the deals, so you're just outright wrong there.

 

Perhaps this would be worth reading, which explains why you - and humans in general - may find it so difficult to understand this: https://cocosci.princeton.edu/tom/papers/hard.pdf

[thepossum]

You seem to be fundamentally misunderstanding what 'randomness' means. If you *couldn't* spot patterns from time to time, that would prove beyond doubt that the hands were *not* random.

 

How do you know. Couldn't it be a very long sequence of "random" hands where nobody spotted any patterns at all. From your logic if occasional patterns in the infinity of randomness are indicative of randomness then so are infinitely long sequences without patterns. Maybe the person observing has a poor sense of pattern observation too. Who knows

 

Pattern matching is an attribute of each individual's brain. How many people have observed patterns etc

 

All I am hoping is that it was demonstrated that the number of people and the patterns they observed were also random etc

 

 

Unless you're referring to some Goulash-style tournaments, which are specifically handcrafted and thus not relevant to this discussion, it has been shown time and time again there is no bias in the deals, so you're just outright wrong there.

I'm not going to ask for details on how they assessed the hands for lack of bias, whatever that would mean anyway :)

 

Just wondering. From you above comments if the randomness consultant showed a set of hands and nobody spotted any patterns if the algorithm had to be changed to ensure there are patterns that you assure me guarantee randomness

 

 

Do I need to go on with this discussion

 

Its a fun topic though. I will see if I can dig up my musings on randomness in Bridge

 

Lets think. I know the number of hands dealt so far is a tiny fraction of infinity etc

[pilowsky]

You will be unsurprised to discover that there is quite a bit of research concerning people’s knowledge about probability as it applies to real life.

I mean, what are the odds that you can make money out of other people misunderstanding things.

 

Here is a table reproduced from one of these studies.

(Regarding) Independence of events

There is a Lottery number that has not come out in the last 10 draws.

Is it more likely to come out on the next draw?

Answer_________N____%___CI

Absolutely no:___759:_57.9:__54.6–61.2

Mostly no:______300:_27.0:__24.0–30.1

Mostly yes:______175:_13.5:_11.4–15.9

Absolutely yes:____23:_1.6:__1.0–2.5

(Tomei A., et al., (2017) Misbeliefs About Gambling in a Convenience Sample from the General Population. J Gambling Studies 33:899-906).

 

More than 40% of people do not understand that the chance of a lottery number being drawn is independent of the numbers drawn previously.

This belief system is not surprising. Elsewhere in this forum, we have discussed various strange beliefs that people hold for one reason or another, even when there is clear evidence to the contrary.

Medical students are taught that “common things occur commonly” and that “if you hear hoofbeats outside the window, think horse, not zebra.” - In Australia anyway.

Students are taught all kinds of mnemonics to help remember common patterns that appear in certain diseases e.g.: fair, fat, forty & female = gallstones.

They don’t tell you (know) the proportion of cases that the so-called typical presentation accounts for (I’m guessing about 10-15%).

 

Two interesting things about randomness. First, life requires a certain amount of variety. If your heart beats monotonically, you’re dead. All the same, the interval between beats is not entirely random - that would also be bad.

The second thing is that the human nervous system has evolved to see shapes and patterns: This ability is useful to bridge players.

A sheep has specialised neurons that activate when they see other sheep and entirely different neurons that fire when they see a sheepdog. If shown the image of a dog that is upside down the neuron fails to fire.

Monkeys are different; they don’t care about the orientation of the threat - but sheep spend minimal time swing around in the trees.

 

If Bridge hands were monotonically different, then as smerriman notes, something would be wrong.

It may or may not be ‘hard’ to learn, but as they say, if you don’t know, you don’t know.

 

To be fair, though, most of the people who write here enjoy collecting masterpoints, an activity that bears little apparent relation to skill.

But, there are other benefits to acquiring masterpoints. There must be. Why else would people bother?

[thepossum]

:lol:

[hrothgar]

Few quick comments here:

 

I am not aware of any well established tests to determine whether or not a large set of bridge hands are sufficiently random. You can certainly test individual hypotheses about the hands (who is getting how many HCPs, are various shapes being dealt in the right proportions, etc.). However, I am not aware of bridge equivalent to the Diehard tests and the like that are used to validate the performance of PRNG's like the Mersenne twister and the the like. People have spent a whole lot of time thinking about how to prove that these are sufficiently random for various purposes.

 

The best way to validate the performance of the BBO hand generators would be inspection of the code base.

 

You want to verify that they

 

1. They are using a high quality PRNG

2. They are using a good method to provide this with seeds

3. The code that transforms the output of the PRNG --> deals is not introducing bias

 

Absent this type of inspection, you're (pretty much) forced to rely on testing a set of different hypotheses about some large number of deals

 

BBO hired a statistician to do just back a years back.

He was happy and content with the results.

BBO has not changed the dealing code base since then.

 

I think that they should publish their code.

[mythdoc]

I think that they should publish their code.

 

I agree. I also think there should be transparency on how the deals get to the various events, be it anonymous play, live games, deal pool, etc, since some (me included) assert that the deals differ among these. A while back I suggested one would notice a difference in hands between a series of “just declare” IMPs challenges and just declare MPs challenges. Probably no one tried this, because we are all stuck in our Rorschach test believing what we want to believe. (I include myself in this.)

[thepossum]

I was searching my hand archives for a clear example of a non random hand

 

It was like join the dots preschool Bridge where every play was a simple and fairly tedious sequence of covers round the table

 

Clearly not random at all. After I noticed it on the first few rounds I just played the whole hand that way

 

Just thinking of ways to test for bias. How about comparing the frequency of all hands dealt so far on Bridgebase with the theoretical uniform distribution of all possible hands

 

P = 0.5 X 10-38 or something

 

I can't remember tests and distributions. Maybe a simple Chi Square test

[smerriman]

I was searching my hand archives for a clear example of a non random hand

Thanks, this is now the best comment I've ever read on BBO.

[thepossum]

Thanks, this is now the best comment I've ever read on BBO.

 

😂

 

I was just thinking of a simple problem with one non random hand. Then we have to look at non random sets or sequences

 

I'm sure we've all had sets of hands which all seemed very similar

[thepossum]

Suppose there were 10^n hands dealt so far.

 

Let's hope for no duplicates

 

How does ChiSquare look

 

When I wake up I will calculate it. Degrees of freedom could be a problem

 

Of course I appreciate a uniform distribution is no guarantee of randomness

 

Sorry if I appear to be at all facetious about demonstrating lack of bias

 

I always used to get anxious about claims that there was almost zero chance of duplicate MAC addresses, and what would or could happen if there were

 

The level of discussion and appreciation of the issue reminds me of the old school level problem of how many people you need to get 50% chance of two with the same birthday. But in this case we have 10^38 order choices

 

And as far as I'm concerned in the infinity of true randomness it doesn't matter what any hand or set of hands are like and how they were dealt. The infinity of true randomness includes totally non random stuff too

 

But does that pass the Bridge pub test

 

In that case do things have to be engineered to ensure enough apparent randomness

 

Also without knowing I imagine hands for different levels of tournaments are designed. Much like golf. You don't want Tiger Woods playing a boring par 3 suburban course etc. They bore me to death and I can hardly hit the ball

[hrothgar]

 

I always used to get anxious about claims that there was almost zero chance of duplicate MAC addresses, and what would or could happen if there were

 

 

Back in the weird old days, MAC addresses were set manually on the cards using pins.

Even now, many drivers allow you to set a MAC address

 

Believe me, duplicate MAC addresses happen (and are a pain in the butt to handle)

 

This used to be a lot worse when stuff was all on a broadcast bus because you'd have two different IPs ARPing the same MAC

[thepossum]

Back in the weird old days, MAC addresses were set manually on the cards using pins.

Even now, many drivers allow you to set a MAC address

 

Believe me, duplicate MAC addresses happen (and are a pain in the butt to handle)

 

This used to be a lot worse when stuff was all on a broadcast bus because you'd have two different IPs ARPing the same MAC

 

I imagined it must happen, never heard what happens it did.

 

And since the Internet of Things or whatever its called etc - how many people have accidentally controlled someone else's device

 

The other amusing things is that some of the people who keep having a go at me over randomness or other stuff here from time to time would assure me that each individual troll attempt were totally independent too :)

[hrothgar]

Suppose there were 10^n hands dealt so far.

 

Let's hope for no duplicates

 

How does ChiSquare look

 

When I wake up I will calculate it. Degrees of freedom could be a problem

 

Of course I appreciate a uniform distribution is no guarantee of randomness

 

Sorry if I appear to be at all facetious about demonstrating lack of bias

 

 

When folks are analyzing whether or not bridge hands are random, they normally look at things a bit differently that you are.

 

It is certainly true that you should NOT expect to see bridge hands occur more than once. However, unless you have a completely pathological hand generator, these sorts of issues normally occur because the process for seeding the PRNG is flawed and not the PRNG process or the hand generator itself. (Note: Because of this - and the way the PRNGs work - duplicate hands occur in runs. If you have one, you end up with a whole bunch in a row)

 

Normally, the sorts of tests that you run look at the distribution of HCPS or the distribution of hand shapes and the like and whether these are biased in some way. A more complex analysis would try and see whether there was some periodicity to these distributions. For example, the total number of HCPs is unbiased, but this is because odd number hands are biased in one direction and even number hands are biased in another.

 

Sadly, there's a near infinite number of ways in which a hand generator might be flawed and testing all of them is expensive. (Its for this reason that I think that code inspection is a much better way to handle these sorts of issues.)

 

If you're interested in taking a deeper dive on this subject, I recommend looking a discussion around the period of a PRNG. You also might want to look at the following tests that have been used to evaluate PRNGs. https://en.wikipedia.org/wiki/Diehard_tests

[pilowsky]

The problem may be more subtle than simply asking, "Are the hands dealt randomly?"

This is a fairly "easy" question. Given that so many hands are dealt and played, it is doubtful that a single individual (even those of us who play hundreds or thousands of hands a week) would detect any non-random pattern or if they did, be able to use it to their advantage.

Remembering that a non-random pattern (as pointed out earlier) is not a series of hands where patterns don't appear from time to time.

A true lack of randomness would exist if the coin turned up "heads" every single time. As Tom Stoppard explained in "Rosencrantz and Guildenstern are dead" when that happens, it is proof that you are dead because it's impossible (like the spade I suppose).

 

All kinds of illusory ideas about randomness pop into one's mind only to be quickly dismissed, either by ourselves or with a few caustic comments on the Forum.

 

In education, there is a different problem: the "quality of candidature".

 

It works like this. In a total population of students undertaking a final examination, it is necessary to generate a single final ranking.

 

This ranking is used in many ways, but one way is to allocate students to their university entrance preferences. The system may differ from jurisdiction to jurisdiction. Still, somehow it is necessary to "moderate" results so that the students that undertake modern European history are ranked in the same way as those studying advanced calculus, biology, legal studies or design.

 

How is this relevant to the topic at hand?

If we look at the Daylongs, there is an anti-cheating measure in place. Each contestant plays 8 boards (in the DL1, for example) played by roughly 30 other players.

This means that I am in a pool of ~240 contestants in a competition where about 1000 people finish.

 

Don't get me wrong - I enjoy my DL1 - even though the Zenith seems to have pinched some of the participants, but:

 

If 1000 people are playing 8 boards each that about 30 other people also play, then 1000 players in the DL1 compete against vastly more players than entrants.

 

This is where we run into the quality of candidature problem. It may not be the deals that are non-random, but it seems that the opponents are.

 

Reductio ad absurdum, imagine for a moment that you are playing a team match against another pair, and you are doing reasonably well when suddenly the pair that you are competing against leaves and Nige1 and shyams step in.

One could argue that as a test of your skill, this is not a bad approach. I'm not so sure.

 

My understanding of how a Bridge competition is meant to work is that the hands are randomised, not the opponents.

Elsewhere, barmar argued that although this may be true, The "good players" consistently do well. What about the rest of us? My results oscillate so wildly it's hard to know who I'm playing against.

Is it a bad result simply because my opponents on the day were all Nige1's, shyams' or kenberg's or are my good results happening through a judicious combination of luck and strangely incompetent opponents.

 

To make the competition fair, it would be necessary to use the same "quality of candidature" tools that the Board of Studies uses to ensure that all students are ranked fairly before the results are passed on to the next stage.

 

If this level of randomness of opposition is truly the case, the tournament might better be described as a race where the runners are completely blind.

In the end, you rank "x" depending on who else showed up on the day.

 

It's satisfying until you learn that every other blind competitor had a completely different pool of opponents: some of whom were using bicycles.

[mythdoc]

You don't want Tiger Woods playing a boring par 3 suburban course etc.

 

You also, certainly, wouldn’t expect a champion golfer to continue to visit your course if its design was so out of date that it sometimes (routinely) allowed bad players to beat him/her with bad plays. The GIB robots need all the help they can get, in my experience.

[blackshoe]

Lets think. I know the number of hands dealt so far is a tiny fraction of infinity etc

"A tiny fraction of infinity" is a nonsense phrase. That tiny fraction is still infinite.

 

Besides we're not talking about infinity. There are only 635 billion possible hands.

[thepossum]

"A tiny fraction of infinity" is a nonsense phrase. That tiny fraction is still infinite.

 

Besides we're not talking about infinity. There are only 635 billion possible hands.

 

The number of hands is finite but the issue of distributions and randomness requires consideration of infinity

 

I need to add a correction. My memory isnt that good. I think I had the number of possible deals wrong by about 10 orders of magintude. Its only around 5.3 x10^28 deals

 

But we are looking at the samples of hands, sequences, many players potentially over an indefinite period of time and much of the theory that is used also requires infinity

 

I still don't think the problem has been specified well enough. Are we allowing for other variables and differences in individual perception of a pattern or lack of randomness too

 

But most of do usually only see a tiny fraction of infinity do we not :)

 

Deleted some nonsense statistical calculations :) I think I totally mis-estimated the degrees of freedom. My brain is addled at the moment

[jardaholy]

OK, Are the Bridge Hands on Bridgebase truly random? Or, are the hands sometimes padded to make the game more interesting?

Well, this is THE question!

I got PhD in probabilistic risk analysis and I earn my money in this area for almost 35 years.

I started playing daylongs at the begining of Covid-19 pandemia and played approximately 30 boards a day, i.e. more than 11000 boards by now so that the data sample is big enough to make some conclusions.

I absolutely do not believe that the boards are truly random.

During last several months, I met the hands with 6-6 distributions seven or eight times, that is far more than it should have been (just one example, other sick distributions as 7-5, 8-4 etc. are also much more frequent that they should have been).

Still, this is not about distribution.

In some discussion here, I could read very nice idea that the variance of the results in the boards generated in daylongs is what is much bigger that it should have been. Just because the boards are not flat, at least many of them.

That is even possible to do - I can imagine that the software for dealing boards for daylongs simply use, for the pool of boards, boards, which already were played sometimes and produced results with high variability (not allowing you to play board, you already played).

Of course, boards with high variance of results must be, in general, more demanding and more interesting than flat boards, where the variance of results is very small (everybody can manage such board and get average result).

The main problem I can see, if it is really the case, is that the boards with high variance of results are biased in some specific ways. For example, you can get high variance of results, if you offer the players a board with significantly sublimited game or slam (which also need good card play) You will not get such big variance in results if such game is impossible to be made. But I do not like that, because it has impact on my bidding and play and I am affraid, I will more frequently overbid the board later, in my bridge club, as soon as it is opened after Covid, just because of bad habit I got here.

If I have not been absolutely sure about what I am writing here right now, I am even more persuaded after playing one very specific board recently (I do not want to present it right now, because it could be still in play at BBO). This was almost a kind of once-per-life board, you should not meet once per month as here. But this one was even more special. The slam (bid by the robot on the opposite side) looked absolutely impossible to be made, but after several minutes, I found the way, it could be made. It needed just a small thing - the distribution 6-6 in the hand of one of the defenders. And it really was that. I am grateful to BBO for having this miracle experience (and a nice story for my bridge friends), but I am still not sure, whether this way of generation of the boards is good.

[hrothgar]

Well, this is THE question!

I got PhD in probabilistic risk analysis and I earn my money in this area for almost 35 years.

I started playing daylongs at the begining of Covid-19 pandemia and played approximately 30 boards a day, i.e. more than 11000 boards by now so that the data sample is big enough to make some conclusions.

I absolutely do not believe that the boards are truly random.

 

All tournaments are not created equal

 

BBO give tournament organizers the ability to screw with the hands.

And, lots of individuals running tournaments choose to do so.

 

If you truly are getting way too many 6-6 pattern and the like, it probably reflects the tournaments that you are playing in rather than the hand generators itself.

 

In order to evaluate the whether or not BBO's hand generator is biased in some manner, you'd want to look at a limited set of tournaments (for example, non best hand tournaments run by the ACBL)

[pilowsky]

Well, this is THE question!

...

 

What are the odds that sitting South you would pick up this hand AND be playing in a major tournament AND be the worlds best Bridge player?

[hv=pc=n&s=shadakqt9865432c6&w=s92hqj97643dcqj85&n=sajt87hk52djct932&e=skq6543ht8d7cak74&d=e&v=n&b=2&a]399|300[/hv]

 

And the lead was a ♠.

one in 2,722,762 apparently.

 

If the current pandemic has (re)taught us anything, it's that incredible 1/100 year events only happen once in a hundred years, but there are lots of them.

COVID-19, Texas freezing, NSW and California burning, A non-white woman being elected to be Vice-President.

The hand may be over, but the war goes on. http://bit.ly/WarGoesOn.

 

It turns out that the odds of being dealt a hand with 9-x-x-x or better are better than 1 in 1700. Last month I played only 750+ hands.

One dealing site has now dealt more than 57,527,618,400 hands

 

26,358,553 of them (0.045874812%) held 25 or more HCP!

 

I've said it before, common things do occur commonly, but uncommon things do occur.

 

 

http://bit.ly/Zia7D

[hv=pc=n&s=shadakqt9865432c6&w=s92hqj97643dcqj85&n=sajt87hk52djct932&e=skq6543ht8d7cak74&d=e&v=n&b=2&a=1s2d2hp2s2n(psych%20%5Bapparently%5D)p3np5hp5np7dppdrppp]399|300[/hv]