2-7 CP Questions!

[AndyatSD]

Hi,

New to posting in this sub-forum but I've been lurking for a while. I just started playing Chinese Poker last month and I’m so addicted. I’ve played on TigerGaming and recently half my weekends at Commerce has been spent on Chinese Poker. I understand the math behind CP high, but last weekend was my first time playing 2-7 CP. I got some guidance from TT and Deathdonkey on this but I still had some more questions and DD suggested I post it in the forum so here goes. Thanks in advance for any pointers! =)

1) What is the average (say, 50%) strength of hand to win the middle low? Intuitively I’d think the breaking point is the worst possible 8 / best possible 9, but I’m not too sure. Also, how big of a difference does going from a medium 8 to a good 9 make? For example, using CP high front hand terms, is the relative difference between going from a 25678 to a 23469 bigger than going from JJ to KK in the front? Is there somewhere to study the math for this?

2) I been following the intuitive strategy of ‘make the best possible low hand without severely crippling yourself, and break minor stuff up if I can make a competitive low’. I had thought that a competitive low worth breaking things up for was like a 9, but DD says even a 9 is a crying call at best and it’s probably better to go for a strong front/back rather than to break up all but the weakest stuffs for the middle. Thoughts on that?

3) This might be wrong, but while I noticed that hand strength in the front severely went up (anyone have the math?) to the point that 22-QQ owns trash and gets owned by anything more legitimate, I did notice that the back average value to win seem to have decreased. I reasoned this is because 20 lowball cards have to be used for the low hands so that greatly decreases the chances of making low straights. Not only that, but since there’s a lot more flexibility in getting the trips up in front, people do that to try to get a more secure lock in one of the three hands, thereby decreasing the chances of fullhouse in the back. The result that I observed was that flushes was much more common in the back. I also think this is because when you have something like 223467889 while the best possible low in that hand is 23467, if you can make a flush with some of the cards and make a 8 or 9 low and you couldn’t otherwise make a single darn thing in the back, you’d go with the flush and the 8 low (9 low a bit closer call)? So if that theory is true, then to me that means the value of the higher cards in the flush has substantially increased. Can anyone confirm/deny?

And all in all if anyone has recommendations on how to do the calculations for a modified win probability table for 2-7 CP I’d greatly appreciate some help. Thanks!

~andy

[MarkGritter]

I wrote a pair of articles forthcoming in the 2+2 magazine about CP2-7 which will answer these questions and a bunch of others. You might also want to check out older posts by me about setting CP2-7 hands, and the data posted at http://lowballgurus.com/ (at the bottom of the page.)

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1) What is the average (say, 50%) strength of hand to win the middle low? Intuitively I’d think the breaking point is the worst possible 8 / best possible 9, but I’m not too sure. Also, how big of a difference does going from a medium 8 to a good 9 make? For example, using CP high front hand terms, is the relative difference between going from a 25678 to a 23469 bigger than going from JJ to KK in the front? Is there somewhere to study the math for this?


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Lowballgurus has a complete percentile hand ranking list resulting from a strong strategy.

In the middle, the median hand is about a 98753.

87652 (which I would consider a poor 8) is about 66th percentile, while 96432 is 64th percentile. They're very close, much closer than JJ and KK (I think).

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2) I been following the intuitive strategy of ‘make the best possible low hand without severely crippling yourself, and break minor stuff up if I can make a competitive low’. I had thought that a competitive low worth breaking things up for was like a 9, but DD says even a 9 is a crying call at best and it’s probably better to go for a strong front/back rather than to break up all but the weakest stuffs for the middle. Thoughts on that?


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It is often incorrect to make the strongest possible middle; going from a 75 to a 76 or from a 7 to a strong 8 is usually worth it if you can significantly increase the front or back.

Nines in general form a very broad range; 95432 is a 65th percentile hand, while 98764 is a 49th percentile. You can sweep with them but because of card-removal effects your opponent(s) will be more likely to make good lows if you can't.

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3) This might be wrong, but while I noticed that hand strength in the front severely went up (anyone have the math?) to the point that 22-QQ owns trash and gets owned by anything more legitimate, I did notice that the back average value to win seem to have decreased. I reasoned this is because 20 lowball cards have to be used for the low hands so that greatly decreases the chances of making low straights. Not only that, but since there’s a lot more flexibility in getting the trips up in front, people do that to try to get a more secure lock in one of the three hands, thereby decreasing the chances of fullhouse in the back. The result that I observed was that flushes was much more common in the back. I also think this is because when you have something like 223467889 while the best possible low in that hand is 23467, if you can make a flush with some of the cards and make a 8 or 9 low and you couldn’t otherwise make a single darn thing in the back, you’d go with the flush and the 8 low (9 low a bit closer call)? So if that theory is true, then to me that means the value of the higher cards in the flush has substantially increased. Can anyone confirm/deny?


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Look for a post from Phat Mack that has a nice graph comparing hand strengths in CP high and CP2-7.

Your intuition about the front is correct; the median hand is QQJ, and even AA2 is only 68th percentile.

I don't have a good feel for CP high so I can't really address your second point directly. The median back in CP2-7 is around an A6432 flush. Straights in back are trash at whatever rank.

[AndyatSD]

Wow, thanks so much for the help Mark! I'll digest all this after dinner. Looks like exactly what I'm looking for, though =)

Such great info! Looking forward to those articles you mention. Thanks again!

~andy

[Phat Mack]

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I wrote a pair of articles forthcoming in the 2+2 magazine about CP2-7 which will answer these questions and a bunch of others.

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I just read the September article and thought it beautifully done.