WSoBJ episode 6

[KenSmith]

Good point Lamar.

This may be a stupid question, but, if Dave needs to win once Bobbie makes bet of $1700 cover low, what makes $3500 a better bet than a max bet? Why not just go max as long as you have enough for a split?

You're on track, because a max bet is better than $3500, since as Lamar points out, $4300 or more covers a blackjack by Bobby.

However, if you REALLY want to get picky, anything between Lamar's recommended $4300 and $4950 is ever so slightly better than $5000, because they still allow Dave to split twice if needed. This would only matter in cases like (8,8) vs 6 or something like that, where splitting improves the chances of winning overall. The extra money is meaningless, but being able to resplit 8s increases the chances of netting at least one bet of profit.

tirle_bj is the resident expert on how to optimally play hands after a split. There are some surprisingly complicated scenarios that he has worked out.

 

[Jackaroo]

Double down on hand 30?

I may be the newest of the newbies registered on this site, having played in a grand total of 2 mini tournaments--and those were just last month.

But I believe there is a math error in dugu's scenario number 3 above. The only way Dave can lose the table is by drawing a 2 thru 6 on his double down. This is a probability of 5/13 = 0.3846 which when expressed as a percent and rounded to the nearest tenth is 38.5%.

--jr

OOPS! After making the post, I realized the 5/13 figure was considering the fact that the dealer already had a made hand of 17. If the dealer busts, Dave's double beats Bobby's. The true situation for Dave to lose is that he has to draw a 2-6 AND the dealer has to make a hand. These are dependent events so we must multiply the probability of drawing 2-6 with the probabiltiy of the dealer making a hand (0.5772 with a 6 up) which gives us 22.2%.

Now I am on the other side of dugu's 32%! Am I missing something else?

--jr

 

[KenSmith]

I believe there is a math error in dugu's scenario number 3 above. The only way Dave can lose the table is by drawing a 2 thru 6 on his double down. This is a probability of 5/13 = 0.3846 which when expressed as a percent and rounded to the nearest tenth is 38.5%.

I can explain where dugu came up with the 32%. Doubling (A,9) vs 6 will lose 32% of the time. This assumes appropriately that we know nothing other than the dealer's upcard of 6.

toonces comments about a double-down card of 2-6 losing for Dave are based on the dealer subsequently having 17. However, I'm really confused now, because the original toonces description of the episode shows that the dealer busted on the final hand! It looks like this idea of the dealer making 17 on the final hand came from a post by TxTourPlayer. Looks like I'll have to replay this episode tonight when I get home.

 

[KenSmith]

These are dependent events so we must multiply the probability of drawing 2-6 with the probabiltiy of the dealer making a hand (0.5772 with a 6 up) which gives us 22.2%.

This underestimates the chance of losing on the double, because (A,9) can draw a card of 7, 8, 9 or ten, and still lose if the dealer draws better. The true percentage, as in dugu's post, is 32%.

 

[dugu]

toonces comments about a double-down card of 2-6 losing for Dave are based on the dealer subsequently having 17. However, I'm really confused now, because the original toonces description of the episode shows that the dealer busted on the final hand! It looks like this idea of the dealer making 17 on the final hand came from a post by TxTourPlayer. Looks like I'll have to replay this episode tonight when I get home.

The dealer shows a hole card A.

 

[dugu]

But I believe there is a math error in dugu's scenario number 3 above. The only way Dave can lose the table is by drawing a 2 thru 6 on his double down. This is a probability of 5/13 = 0.3846 which when expressed as a percent and rounded to the nearest tenth is 38.5%.

The computation is as follows:
P(dealer beats dave) = P(dealer 17)*5/13+P(dealer 18)*6/13+P(dealer 19)*7/13+P(dealer 20)*8/13+P(dealer 21)*12/13
~= 16%*5/13+10%*6/13+10%*7/13+10%*8/13+10%*12/13 ~= 32%.
Each number might be off up to 1%.

 

[Jackaroo]

My probability computation errors

Thanks dugu. The breakout for each possible dealer hand makes clear that I was indeed missing something else. After correcting my original mistake of not considering dealer hands >17 I still erred by limiting the player hand to the 5 cards making a total of <17 for each outcome!

BTW, anyone, how do you reply with a partial quote from a previous post? When I click the Quote button the entire post is included in the message box with no separation from any text I might add. Are there instructions anywhere on the site?

--jr

 

[KenSmith]

How to partially quote

BTW, anyone, how do you reply with a partial quote from a previous post?

After you click the quote button, just manually delete the sections that you want to remove of the quote. Just make sure that the final version of your quote starts with

and ends with [*/quote] except leave out the * in the closing tag. (I used that to keep the quote tags from being interpreted in this message.)

I'm acutely aware that navigating around and posting on a message board involves a set of non-obvious skills. All I can do is encourage you to experiment. If you mangle a post and would like help editing it, just let me know, either by a second post, a private message, or an email.

 

[Agent0042]

Hmm. I knew how to do quote before, but I didn't know that you could put in =username to add in the username. Thanks for the tip on that one.

 

[toonces]

toonces comments about a double-down card of 2-6 losing for Dave are based on the dealer subsequently having 17. However, I'm really confused now, because the original toonces description of the episode shows that the dealer busted on the final hand! It looks like this idea of the dealer making 17 on the final hand came from a post by TxTourPlayer. Looks like I'll have to replay this episode tonight when I get home.

Tx was right. That detail didn't matter on the final hand, and in the rush to post and get to sleep, I got that wrong

 

[KenSmith]

Tx was right. That detail didn't matter on the final hand, and in the rush to post and get to sleep, I got that wrong

So did Max Rubin! I replayed this last night. After the dealer turned over the Ace in the Hole, Max said something about the dealer busting. It was a little garbled, but if you get a chance, replay it and see what you hear.

 

[Agent0042]

I don't have anything but the closing credits on tape myself, but I think there's at least one more repeat. I'm definitely going to listen for that.

Actually, I sure hope they repeat the entire run after next week's show.

 

[tirle_bj]

tirle_bj is the resident expert on how to optimally play hands after a split. There are some surprisingly complicated scenarios that he has worked out.

Ken, thank you for a compliment, but "how to play hands after split to win two bets" is originally your idea. It was posted by you in BJ Confidential - perfect research. I just doublechecked it and added the case when double after split is permitted and you have enough funds to do that.

Anyway, here's very interesting situation, when R.R. was trying to win his hand (7,7) vs 9. This is the situation when after split we need to win only one bet. So we're trying to break a new ground here. See in "tournament strategies and teasers"

 

[KenSmith]

Yes, reruns are coming.

Actually, I sure hope they repeat the entire run after next week's show.

A brief conversation I had with someone at GSN recently indicated that they would be rerunning the entire series. No surprise there, since I'm sure they'll want to get as much mileage as possible out of it.

 

[KenSmith]

The computation is as follows:
P(dealer beats dave) = P(dealer 17)*5/13+P(dealer 18)*6/13+P(dealer 19)*7/13+P(dealer 20)*8/13+P(dealer 21)*12/13
~= 16%*5/13+10%*6/13+10%*7/13+10%*8/13+10%*12/13 ~= 32%.
Each number might be off up to 1%.

As a hopefully useful resource for these kinds of questions, I've just posted a complete table of double down probabilities at
http://www.blackjackinfo.com/bjtourn-doublechart.php

Doubling (Ace,9) vs 6 like in this situation has these results:
Win: 60.934%
Push: 6.800%
Lose: 32.266%

dugu's number was right-on, but now he won't have to do the math next time.