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If we want to promote bridge to young players and school children we need to change the image of bridge as a retiree's game.

We could look at chess to see how to run a successful program. In chess there are scholastic tournaments for K-12 students only. A state tournament could usually draw hundreds of players and Super National (once every four years) draws over 5000 players. Successful young players will move on and playing in open tournament with adults.

I started to teach a group of young students this year. I found most difficult part is to providing them an environment they could play outside of class. There are a lot of activities available to today's kid. They might want to go to a swimming program and stopped to come for bridge. I lost one student because of that. We need to make our game more attractive.

Kids are fond of new technology. We could explore ways to use technology to draw them to the game. For example there are two websites: chess.com and chesskid.com. They are developed by the same company. If you look at the chesskid.com, you would easily see why it is more appealing to kids. You could organize kids only game, giving awards(badges and trophies) etc.

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Alan, I agree with you we need a MP system and a rating system. MP is a reward system that encourages players to play. Rating is used to stratify players to create better match condition.

Rating system is not going to turn players away from the game. In fact chess rating has seen an increase of player in tournament play. The reason is finer stratification allows players to match with others in the same level and gave player a better experience. If you look at chess tournament, it has more stratification (class) than bridge.

I think a rational system would use a rating system to determine stratification and seeding. Masterpoint is rewarded for each stratum top finishers.

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Tom, I agree with you that masterpoint is an incentive for beginners and intermediate players. However after certain point it has lost its attraction because of the inflation. You could find the evidence from the ACBL statistics you quoted.

If you look at the large population of a given masterpoint range. It is 300-400 (>9,000). It is a clear indication players stopped playing after they get LM (old requirement of 300). With new requirement of 500, we might see it move up gradually. There are also similar effect at other level like 1000. However it is most striking at 300 if you compare with the level below it.

I have not received this survey and I wonder why ACBL does not do a survey on player who stopped playing to find out what could make them to play their game. I know a few players who stopped playing in ACBL tournament, but not stop playing bridge. They still play on BBO.

Just like you I don't have a lot of masterpoint(~800), I've already found this is not an attractive system for me and I have no incentive to play even in regional. The only event that could attract me is NABC but there is only three times a year.

Instead of playing more, I decided to teach some kids to play bridge since the beginning of this year. So far I have 16 of them (age 10-13) completed the 21st Century bidding class. I found this experience is more rewarding.

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Yes. If you read the minutes. It mentioned they looked at my rating proposal but did not endorse it. It is a big change for them and I'm not sure everyone on that committee understand the details since they never asked me any follow-up questions.

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I think everyone here agree more level by masterpoint is meaningless and probably only has very limited effect to induce players to play more. In addition, masterpoint could not be used as a measure of player's strength.

If ACBL want to use reward to get players to play more game, I would suggest creating some new pigmented points. The gold point is too easy to get now, especially with the proliferation of KO events. Platinum point has some real meaning but there is only three times a year you could get it and not every player could play in NABC. So one solution is to create a new “real gold” that is award only to Open event (pair or Swiss team) at regional level. This is more like the original “gold” point. The other is to create a new category for National rated Limited event if we want more players to play those events.

Another idea is to go away from master point but have something like the “Norm” in chess. In fact we've already had something like that called Ribbon Qualification. However this information is not published. In chess “Norm” is something you need to get in order to get a title of IM or GM in additional to rating requirement. You get “Norm” by playing in tournament where you play against a certain minimum number of IM/GM and achieve a certain winning percentage. Since current MP only award top finishers, it discourages players not in top tier to play in open event at regional. Something like “Norm” could be obtained without being top finisher as long as you played against to strong field with reasonable results, so it could encourage more players to play in open events.

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In chess rating system, a rating difference of 400 predict strong player should have a expected score of 0.9 per game. It means win 9 and lose 1, or win 8 and draw 2.

In my system, I could use 4 pair's rating to calculate an expected score of MP/board or IMP/board. Of course, this is still to be tested with large data set.

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OK. I think in this case, per board and “session” does not make much difference.

However what other rating program including EBU are using “section” data. That is a game with 24 or 27 boards typically and players played against a number of opponents. This is what Chris Champion uses.

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For the first question, I'll revise my questions as what are the successful rate playing for finesse vs dropping?

On your question, since the choice is play A or Q. My determine factor would be who has the K. Who has J does not matter. If 10 is singleton, it does not matter which one to play. However if LHO has all three cards, if does not matter (with a condition you have no entry problem). So my decision is if K is on the left I should play Q, if K is on the right I should play A.

In order to make decision about relative odd for K, I need to know how many unknown cards in each sides. Taking an extreme case of six cards ending and all of them are unknown. The odds are 6:5 for RHO to have K. So I'll play A. However any information about known cards could greatly change the odds here.

For our discussion about 6 card with J in West, if the question is East and West played ANY spot cards on first round, I agree the odd would be 2:1. Because any spot cards are indistinguishable and it is like Murat's Gold/Silver coin. In Balloon case, if the question is Bob and Alice plays any non-Red, it would be 2/3 because it is changed the coin problem. If the condition is Bob plays Green and Alice plays Blue, it would be different because these two balloons has to be distributed in particular way in initial position. However this is a question more theoretical than practical.

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Nate, I agree the result maybe coincidental. I also want to offer another test case.

Let's assume in a suit your are missing Qxxxx and from previous play you know LHO has 3 cards in the suit and RHO has 2. You need to decide finesse or drop. Question: Is the odd for finesse 60% and 40% for dropping? I'll give my answer later.

For your question, I have to ask may unknown cards there are in each of the hands. I could not calculate odds without it.

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David, finally we could agree on something. This is why I asked what kind of probability you are trying to calculate. If your question was what is the chance for playing Dropping J from East, I would have agreed with you from beginning it should be 1/3. As I described for playing dropping of Kx. When there are 13 cards, the odd is 52%. However if a lot of card has played and only 2 cards left and you played and LHO followed low, the odds for dropping K would be 2/3.

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David, I could understand your feeling and I think we are getting to the bottom it on if the first round of play changes the probability or not. Since there are only 15 limited combinations I'll list them here: 1) W: J654, E: 32 2) W: J653, E: 42 3) W: J652, E: 43 4) W: J643, E: 52 5) W: J642, E: 53 6) W: J632, E: 54 7) W: J543, E: 62 8) W: J542, E: 63 9) W: J532, E: 64 10) W: J432, E: 65 11) W: 6543, E: J2 12) W: 6542, E: J3 13) W: 6532, E: J4 14) W: 6432, E: J5 15) W: 5432, E: J6

What does the first round of heart play do? If you see West plays 2 and East plays 3. You know the original distribution must be from 3), 5), 8) and 12). Other possibilities are ELIMINATED.

You could try you 20 different spot card combination. In each case, you will find 11 were eliminated and only 4 are possible.

If you could not agree that fact that the first round of play means East and West must be dealt with the corresponding cards from initial position, then we are not speak the same language.

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Monty Hall problem is different. It is not completely random. There is a restrictive choice. If you read my early comment about this problem. I also think it could be a restrictive choice problem.

However we are just discussing a pure probability problem here. Let me see if I could try a different way to explain it.

With West having 4 and East having 2, initially there are C(6,2) = 15 ways to distribute the card. Let's think about what the first round a card play means. Let's assume West plays 2 and East plays 3. Now it means in initial card distribution West must have 2 and East must have 3. If you apply these conditions, you'll find only 4 out of 15 satisfy this condition.

What about the rest? The rest cases are 1) East dealt with 3 and 2. There is only 1 way and J is in West. 2) West dealt with 3 and 2. There are 6 ways and it is 50% chance West has J. 3) East dealt with 2 and West dealt with 3. There are 4 ways and 75% chance West could have J. So in these cases eliminated by first round play, the chance West having J is 1/11*100% + 6/11*50% + 4/11*75% = 7/11 = 63.6%

If you are to calculate initial probability, you will find it is

63.6% * 11/15 (cases eliminated by first round play) + 75% * 4/15 (cases remained after first round of play) = 10/15 = 2/3!

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Wei-Bung, we are not talking about the same question. You are correct there were 20 possible ways opponent could play first round of heart. This is before the cards were played. We are in a multiverse where all possibility exist. Once the first round of cards are played, you are in one of these 20 and it is a universe. For example, if you see west played 3 and East played 2, then you eliminate the possibility West could have 2 or East could have 3 in your initial set of combinations. What the probability I ask for is after seeing these card from first round of play what is the chance West or East having J. If this is not what you talked about, we are comparing apple with orange.

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David, it looks like you still did not grasp the point of what the one round of heart play means in probability calculation.

If you don't want to do what I suggested but insist in what you deals randomly, it is fine. Now I'm going to instruct West to play 2 and East to play 3 or whatever 2 spot card combination you choose. Now you count how many time you could see West played 2 and East played 3. If you could not get to this step, you cannot go to next step.

This is same as in your later example, the question is what card West played. Your missing card is K32, so the possibility is 1) W: K2, E:3 2) W: K3, E:2 3) W: 32, E:K

Before you see what card West played, it is 2:1 West having the K. Once West play a card, for example you see it played 2. Then 2) is eliminated because it is improbable any more.

If you don't believe this, think about what you would play in a suit where you only miss Kx. Finesse or drop? I believe we were all told you should play for drop because it has 52% of chance. Why 52%? Each hand has 13 cards. When you play a card, if your LHO plays K, you don't have a decision to make. If he shows out, you don't have a decision to make. If he plays x, the information you gained is he has this card. Now there are still 12 unknown on the left and 13 unknown on the right. So the possibility RHO has K is 13/(12+13) = 52%. If you ignore this fact and asking what the initial odds are for 1-1 distribution. It is 50%. You would have draw the conclusion that finesse and drop has the same percentage rate.

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Lior, even though I don't have direct comparison for rating by board vs by session. Christ Champion and I did some comparison for our rating results in the past. We took a sample of set of games (so we have a controlled data set) and ran our rating program based on same data set. His rating is using session data also adjusted by field strength. My rating is based on board results.

The comparison is tricky because his rating is a percentage and my result is a number. In addition he dropped off certain percentage of lowest rated players. So I compared results by just comparing players from top to bottom. The result is we have an agreement of 50%. What it means is that if I count the top 10 players we have 5 overlapped (50% agreement), if I count top 20, 10 of them overlap.

Since I know my calculation better I could explain to you how using session results would differ in my calculation. For IMP game, the best data I could find from ACBL land is from Swiss team. For Swiss team games, I could extract data about how many boards played and net IMP win/loss. Even though it does not have board level data, I could use this aggregated data to calculate rating and get the same result as using board level data. However there is a condition here is that the players could not change for these boards. If player changes I must recalculate the expected score with board calculation. In case of session calculation I think you have to make some kind of average adjustment. So I could see they would produce different results.

In case of pair event, the opponent changes every round. So the calculation from board vs session would more likely yield different results. It depends on the strength of the players. If all players are in similar strength, the difference could be small. If it varies a lot, I think the results could be quite different because the simple average adjustment from session result would be inadequate.

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David, I know why you could not understand my point. The probability Murat and I calculated is the probability West having J AFTER one round of Heart play. You are keeping talking about the probability BEFORE this round of Heart play.

If you want to do an experiment, you need to alter the experiment this way. Given a spot card one each to East and West, instruct them to play it on first round. The reshuffle and deal the rest of card and count statistics. I would assure you out of 3,000 trial, about 2,250 would have West having J.

The problem is each card in the deck is distinguishable. If West played 2 and East played 3, West must be dealt with 2 and East must be dealt 3. In your initial random distribution you have cases where East has 2 or West has 3. With those distribution West could not play 2 and East could not play 3 at the 1st round. You could pick up any other 2 spot cards but it would produce the same results.

Ping Hu

We could look at chess to see how to run a successful program. In chess there are scholastic tournaments for K-12 students only. A state tournament could usually draw hundreds of players and Super National (once every four years) draws over 5000 players. Successful young players will move on and playing in open tournament with adults.

I started to teach a group of young students this year. I found most difficult part is to providing them an environment they could play outside of class. There are a lot of activities available to today's kid. They might want to go to a swimming program and stopped to come for bridge. I lost one student because of that. We need to make our game more attractive.

Kids are fond of new technology. We could explore ways to use technology to draw them to the game. For example there are two websites: chess.com and chesskid.com. They are developed by the same company. If you look at the chesskid.com, you would easily see why it is more appealing to kids. You could organize kids only game, giving awards(badges and trophies) etc.

Ping Hu

Rating system is not going to turn players away from the game. In fact chess rating has seen an increase of player in tournament play. The reason is finer stratification allows players to match with others in the same level and gave player a better experience. If you look at chess tournament, it has more stratification (class) than bridge.

I think a rational system would use a rating system to determine stratification and seeding. Masterpoint is rewarded for each stratum top finishers.

Ping Hu

If you look at the large population of a given masterpoint range. It is 300-400 (>9,000). It is a clear indication players stopped playing after they get LM (old requirement of 300). With new requirement of 500, we might see it move up gradually. There are also similar effect at other level like 1000. However it is most striking at 300 if you compare with the level below it.

I have not received this survey and I wonder why ACBL does not do a survey on player who stopped playing to find out what could make them to play their game. I know a few players who stopped playing in ACBL tournament, but not stop playing bridge. They still play on BBO.

Just like you I don't have a lot of masterpoint(~800), I've already found this is not an attractive system for me and I have no incentive to play even in regional. The only event that could attract me is NABC but there is only three times a year.

Instead of playing more, I decided to teach some kids to play bridge since the beginning of this year. So far I have 16 of them (age 10-13) completed the 21st Century bidding class. I found this experience is more rewarding.

Ping Hu

Ping Hu

If ACBL want to use reward to get players to play more game, I would suggest creating some new pigmented points. The gold point is too easy to get now, especially with the proliferation of KO events. Platinum point has some real meaning but there is only three times a year you could get it and not every player could play in NABC. So one solution is to create a new “real gold” that is award only to Open event (pair or Swiss team) at regional level. This is more like the original “gold” point. The other is to create a new category for National rated Limited event if we want more players to play those events.

Another idea is to go away from master point but have something like the “Norm” in chess. In fact we've already had something like that called Ribbon Qualification. However this information is not published. In chess “Norm” is something you need to get in order to get a title of IM or GM in additional to rating requirement. You get “Norm” by playing in tournament where you play against a certain minimum number of IM/GM and achieve a certain winning percentage. Since current MP only award top finishers, it discourages players not in top tier to play in open event at regional. Something like “Norm” could be obtained without being top finisher as long as you played against to strong field with reasonable results, so it could encourage more players to play in open events.

Ping Hu

The ranking committee is chaired by Claire Jones. You could find a list of members from this web page.

http://www.acbl.org/about-acbl/administration/board-of-directors/meeting-motions-and-minutes/

They had a report at New Orleans. See following link.

http://www.acbl.org/acbl-content/wp-content/uploads/2015/04/Attachment-D.pdf

Ping Hu

http://bridgewinners.com/article/view/fred-uptons-31-imp-falsecard/

Ping Hu

In my system, I could use 4 pair's rating to calculate an expected score of MP/board or IMP/board. Of course, this is still to be tested with large data set.

Ping Hu

Ping Hu

However what other rating program including EBU are using “section” data. That is a game with 24 or 27 boards typically and players played against a number of opponents. This is what Chris Champion uses.

Ping Hu

On your question, since the choice is play A or Q. My determine factor would be who has the K. Who has J does not matter. If 10 is singleton, it does not matter which one to play. However if LHO has all three cards, if does not matter (with a condition you have no entry problem). So my decision is if K is on the left I should play Q, if K is on the right I should play A.

In order to make decision about relative odd for K, I need to know how many unknown cards in each sides. Taking an extreme case of six cards ending and all of them are unknown. The odds are 6:5 for RHO to have K. So I'll play A. However any information about known cards could greatly change the odds here.

For our discussion about 6 card with J in West, if the question is East and West played ANY spot cards on first round, I agree the odd would be 2:1. Because any spot cards are indistinguishable and it is like Murat's Gold/Silver coin. In Balloon case, if the question is Bob and Alice plays any non-Red, it would be 2/3 because it is changed the coin problem. If the condition is Bob plays Green and Alice plays Blue, it would be different because these two balloons has to be distributed in particular way in initial position. However this is a question more theoretical than practical.

Ping Hu

Let's assume in a suit your are missing Qxxxx and from previous play you know LHO has 3 cards in the suit and RHO has 2. You need to decide finesse or drop. Question:

Is the odd for finesse 60% and 40% for dropping?

I'll give my answer later.

For your question, I have to ask may unknown cards there are in each of the hands. I could not calculate odds without it.

Ping Hu

Ping Hu

If you asks for is when your play the 2nd round of ♥ and LHO played a low heart, what is the probability West to have J, it would be 2/3.

Again it proves every card played changes odds.

Ping Hu

1) W: J654, E: 32

2) W: J653, E: 42

3) W: J652, E: 43

4) W: J643, E: 52

5) W: J642, E: 53

6) W: J632, E: 54

7) W: J543, E: 62

8) W: J542, E: 63

9) W: J532, E: 64

10) W: J432, E: 65

11) W: 6543, E: J2

12) W: 6542, E: J3

13) W: 6532, E: J4

14) W: 6432, E: J5

15) W: 5432, E: J6

What does the first round of heart play do? If you see West plays 2 and East plays 3. You know the original distribution must be from

3), 5), 8) and 12). Other possibilities are ELIMINATED.

You could try you 20 different spot card combination. In each case, you will find 11 were eliminated and only 4 are possible.

If you could not agree that fact that the first round of play means East and West must be dealt with the corresponding cards from initial position, then we are not speak the same language.

Ping Hu

However we are just discussing a pure probability problem here. Let me see if I could try a different way to explain it.

With West having 4 and East having 2, initially there are

C(6,2) = 15 ways to distribute the card. Let's think about what the first round a card play means. Let's assume West plays 2 and East plays 3. Now it means in initial card distribution West must have 2 and East must have 3. If you apply these conditions, you'll find only 4 out of 15 satisfy this condition.

What about the rest? The rest cases are

1) East dealt with 3 and 2. There is only 1 way and J is in West.

2) West dealt with 3 and 2. There are 6 ways and it is 50% chance West has J.

3) East dealt with 2 and West dealt with 3. There are 4 ways and 75% chance West could have J.

So in these cases eliminated by first round play, the chance West having J is

1/11*100% + 6/11*50% + 4/11*75% = 7/11 = 63.6%

If you are to calculate initial probability, you will find it is

63.6% * 11/15 (cases eliminated by first round play) + 75% * 4/15 (cases remained after first round of play) = 10/15 = 2/3!

Ping Hu

Ping Hu

If you don't want to do what I suggested but insist in what you deals randomly, it is fine. Now I'm going to instruct West to play 2 and East to play 3 or whatever 2 spot card combination you choose. Now you count how many time you could see West played 2 and East played 3. If you could not get to this step, you cannot go to next step.

This is same as in your later example, the question is what card West played. Your missing card is K32, so the possibility is

1) W: K2, E:3

2) W: K3, E:2

3) W: 32, E:K

Before you see what card West played, it is 2:1 West having the K. Once West play a card, for example you see it played 2. Then 2) is eliminated because it is improbable any more.

If you don't believe this, think about what you would play in a suit where you only miss Kx. Finesse or drop? I believe we were all told you should play for drop because it has 52% of chance. Why 52%? Each hand has 13 cards. When you play a card, if your LHO plays K, you don't have a decision to make. If he shows out, you don't have a decision to make. If he plays x, the information you gained is he has this card. Now there are still 12 unknown on the left and 13 unknown on the right. So the possibility RHO has K is 13/(12+13) = 52%. If you ignore this fact and asking what the initial odds are for 1-1 distribution. It is 50%. You would have draw the conclusion that finesse and drop has the same percentage rate.

Ping Hu

The comparison is tricky because his rating is a percentage and my result is a number. In addition he dropped off certain percentage of lowest rated players. So I compared results by just comparing players from top to bottom. The result is we have an agreement of 50%. What it means is that if I count the top 10 players we have 5 overlapped (50% agreement), if I count top 20, 10 of them overlap.

Since I know my calculation better I could explain to you how using session results would differ in my calculation. For IMP game, the best data I could find from ACBL land is from Swiss team. For Swiss team games, I could extract data about how many boards played and net IMP win/loss. Even though it does not have board level data, I could use this aggregated data to calculate rating and get the same result as using board level data. However there is a condition here is that the players could not change for these boards. If player changes I must recalculate the expected score with board calculation. In case of session calculation I think you have to make some kind of average adjustment. So I could see they would produce different results.

In case of pair event, the opponent changes every round. So the calculation from board vs session would more likely yield different results. It depends on the strength of the players. If all players are in similar strength, the difference could be small. If it varies a lot, I think the results could be quite different because the simple average adjustment from session result would be inadequate.

Ping Hu

If you want to do an experiment, you need to alter the experiment this way. Given a spot card one each to East and West, instruct them to play it on first round. The reshuffle and deal the rest of card and count statistics. I would assure you out of 3,000 trial, about 2,250 would have West having J.

The problem is each card in the deck is distinguishable. If West played 2 and East played 3, West must be dealt with 2 and East must be dealt 3. In your initial random distribution you have cases where East has 2 or West has 3. With those distribution West could not play 2 and East could not play 3 at the 1st round. You could pick up any other 2 spot cards but it would produce the same results.