Doubling down on Blackjack in 6:5

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March 4th, 2010 at 8:17:04 PM permalink
wildqat Member since: Nov 11, 2009 Threads: 4 Posts: 157	Quote: boymimbo You read the chart wrong. Actually, I had a massive brain fart and figured the EV of a BJ to be 1 less than it should have been. My bad.

March 5th, 2010 at 7:24:33 AM permalink

Jumboshrimps

Member since: Jan 11, 2010
Threads: 8
Posts: 55

Quote: boymimbo
Take a look at the chart above. And let's simplify things and say that you are betting $10 and the dealer shows a 6.

Taking the blackjack wins $12.
Whether you decide to hit or double 21 you would always take one card on a six.

Hitting blackjack wins, on average, $3.337.
Doubling blackjack wins, on average, double: $6.674
You don't win $13.34 (.6674 x 20).

Here is the table that makes up the result of hitting blackjack. It is off a little bit because I am using the Wizard's appendix 2 which takes the dealer probability for 8 decks S17.

Your hand Dealer 17 18 19 20 21 Bust Total
Hand Probability .16564 .10621 .10639 .10159 .09725 .42292 1
12-16 5/13 Lose Lose Lose Lose Lose Win -.05929
17 1/13 Push Lose Lose Lose Lose Win .00088
18 1/13 Win Push Lose Lose Lose Win .02180

19 1/13 Win Win Push Lose Lose Win .03815

20 1/13 Win Win Win Push Lose Win .05415
21 4/13 Win Win Win Win Push Win .27778

Total 1 .02548 .00000 -.01637 -.03126 -.06732 .42292 .3335

The expected value for hitting is 1/2 as much as doubling.

When you hit or double 11 you have a better chance of getting 12-16 than you do 21. The dealer only busts 42% of the time. On the other 58% of the time, the dealer has a chance of beating or pushing you.

Outstanding! I get it now. A bird in hand is better than a drunken bird at Bill's Gambling Hall & Saloon doubling down on blackjack.

March 5th, 2010 at 1:26:35 PM permalink

teddys

Member since: Nov 14, 2009
Threads: 99
Posts: 2707

Quick question, kinda off topic:

What is the advantage of doubling down in blackjack? Is it because you win more double downs than you lose, thus gaining an advantage? What has been said here seems to me that you lose more often than you win DDs.

"If you can make one heap of all your winnings / And risk it on one turn of pitch-and-toss / And lose, and start again at your beginnings / And never breathe a word about your loss..." -Rudyard Kipling

March 5th, 2010 at 1:37:24 PM permalink

cclub79

Member since: Dec 16, 2009
Threads: 26
Posts: 939

You don't lose more double downs (if only done when the strategy is correct), or else it wouldn't be beneficial to ever double down. It's just that in the case of a blackjack, you've already won 1.5 units, so it's not beneficial to risk a 150% win to get a 200% win. If you bet 10 bucks, you are throwing away 15 (plus risking your now safe original ten) to have a shot at winning only 20 (while risking an additional 10). Should be pretty easy to see why it's a bad call.

If you have 11 and the dealer is showing a 6, you will win more than 50% of the time by drawing only one card, which means it's a good time to risk an additional wager to take advantage of that.

March 5th, 2010 at 1:41:13 PM permalink

Jumboshrimps

Member since: Jan 11, 2010
Threads: 8
Posts: 55

Quote: teddys
Quick question, kinda off topic:

What is the advantage of doubling down in blackjack? Is it because you win more double downs than you lose, thus gaining an advantage? What has been said here seems to me that you lose more often than you win DDs.

Any positive number in appendix 9 (or the table applicable to the game you're playing) indicates that, on average, you are more likely to win money than to lose by taking that action.

In more accessible terms, doubling-down is a good move in certain situations because, when you are holding better cards than the other guy, you want to bet as much as possible.

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