Blackjack probability question for BJ players

pokeraddict

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I am not as good at figuring out math when it comes to blackjack so I ask that those who are great at it help me.

I played blackjack at a place I felt was fishy because the dealer kept having 20 or blackjack dealt so I decided I would come back again later and start to track the play.

In session 1 I played 230 hands I counted each time both of us were dealt 20 or BJ. In 230 hands the dealer had 16 blackjacks, I had 4. The dealer dealt himself 29 20's, I was dealt 20 14 times. I emailed and asked for the logs and got them very quickly.

In session 2 I played exactly 200 hands. The dealer had 14 blackjacks, I had 2. The dealer was dealt 20 32 times, I was dealt 20 11 times. I have emailed the casino and asked for logs to this session repeatedly and have yet to have a response.

Obviously the results are very screwed up. Do I have enough hands to make this mathematically useful? Do I need more hands? What are the probabilites of the above results? Thank you in advance.
 

GrandMaster

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The probability of getting 6 or fewer BJ's in 430 hands is between 0.00011 (1 deck) and 0.00014 (8 decks). The probability of getting 30 or more BJ's in 430 hands is between 0.024 (8 decks) and 0.029 (1 deck).

When you talk about dealing 20s, do you mean just the first two cards?
 

pokeraddict

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Yes I only counted the first 2 cards. I counted A9 or two 10 value cards. I already assume the dealer will get more 20's since he will draw more often thus making that kind of useless info.
 

Clayman

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GrandMaster said:
The probability of getting 6 or fewer BJ's in 430 hands is between 0.00011 (1 deck) and 0.00014 (8 decks). The probability of getting 30 or more BJ's in 430 hands is between 0.024 (8 decks) and 0.029 (1 deck).
Would you agree that, given 36 BJ's, the odds of the player getting 6 or fewer is about 1 in 28,700?

It's not like the total number of BJ's is that far off.

Obviously losing 25 units in 430 hands ain't no big deal. Wish that was all I lost yesterday.
 

GrandMaster

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The probability of being dealt 25 or fewer 20's in 430 hands is between 0.00036 (8 decks) and 0.00078 (1 deck). The probability of being dealt 61 or more 20's in 430 hands is between 0.00041 (1 deck) and 0.00082 (8 decks).

If you count BJ's and 20's together, it gets worse. The probability of being dealt 31 or fewer BJ's or 20's in 430 hands is between 0.00000024 (8 decks) and 0.00000048 (1 deck). We are talking about probabilities between 1 in 4 million and 1 in 2 million. The probability of being dealt 91 or more BJ's or 20's in 430 hands is between 0.00047 (1 deck) and 0.00082 (8 decks).

The results are indeed very suspicious. Would you share with us what software it was, or at least PM me if you don't want to make it public?
 

pokeraddict

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I pm'd the casino where this game took place to Grandmaster. For now I do not wish to start trouble, especially because they are a sportsbook and I have NFL futures on who will win Superbowl, one team I bet has a great chance as a 35-1 underdog so I dont want to start public trouble.

Should I email them this thread and ask them to explain how my 2 tracked sessions were possible? Should I go back and get more hands (betting $1 a hand now) to make it more mathmatically useful? I have beaten this game in the past, and I have played many many hours before busting in the past too. The last few sessions just seemed impossible which is why I decided to track it.
 

cipher

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pokeraddict said:
I pm'd the casino where this game took place to Grandmaster. For now I do not wish to start trouble, especially because they are a sportsbook and I have NFL futures on who will win Superbowl, one team I bet has a great chance as a 35-1 underdog so I dont want to start public trouble.

Should I email them this thread and ask them to explain how my 2 tracked sessions were possible? Should I go back and get more hands (betting $1 a hand now) to make it more mathmatically useful? I have beaten this game in the past, and I have played many many hours before busting in the past too. The last few sessions just seemed impossible which is why I decided to track it.
I sure as hell wouldn't go back for more of the same. I'd hav't to think that Jersey's guess is a pretty solid one. Have a good one.
 

Clayman

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pokeraddict said:
Should I email them this thread and ask them to explain how my 2 tracked sessions were possible? Should I go back and get more hands (betting $1 a hand now) to make it more mathmatically useful? I have beaten this game in the past, and I have played many many hours before busting in the past too. The last few sessions just seemed impossible which is why I decided to track it.
Well I wouldn't worry about it all that much - I guess overall I wouldn't go so far as to classify it as "very suspicious". After all, the total number of BJ's and 20's aren't that far off. And, overall, being down 25 units is nothing. And you say you've played in the past with nothing apparently crazy.

I'm not sure what the point of combining these 2 probabilities is either. I mean if I'm dealt the same 2 cards twice in a row against the same dealer up card, the odds are billions to one but so what. I think this should be analyzed as 2 separate events. So I get 1 in 6800 (8D) for the player BJ's and 1 in 810 for the 20's. Or even 1 in 2800 for 20's, your worst number.

Maybe it's just what questions you ask. What if one just asked what are the chances of 36 BJ's or 86 20-totals in 860 hands? Like 1 in 20 or so for each, right?

I'd still get the logs for these 2 sessions and ones in the future if you decide to play more.

GM - I'm getting higher chances of player 20 than you - what prob are you using? (I'm using .01134 for A,9 & .08911 for 10,10 for 6D from a table.)

As a side-question, what would you find to be the most overall fair indicator for a fair game? I guess I always think it's units up or down over hands played in the absence of first 2 cards vs dealer upcard.
 

pokeraddict

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I have had a massive win and a couple of smaller ones. I am still waiting on the other logs. Like I said everything else was normal, or maybe it was even in my favor more then normal. I will look into this when i get the logs for session two. This is why I didnt put the places name in the post. The loss is not all that staggering, just the number of BJ's and 20's for the dealer were impossible. I had a lot of lucky hits into his 20's too to help with some of them. I have to think something is off for there to be such odd outcomes on different days. I will wait a few days and try again and see what happens.

I guess if the loss is in the expected range it does not really matter what gets dealt to determine fair.

As a side-question, what would you find to be the most overall fair indicator for a fair game? I guess I always think it's units up or down over hands played in the absence of first 2 cards vs dealer upcard.

Units up or down is my vote
 

pokeraddict

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I played with my winnings off the game last night and had a very normal game. In exactly 100 hands I had 5 BJ's, he had 4. We were dealt 20 exactly the same number of times and just as before the splits, doubles and busts were normal and I lost .5 units which is about exactly what it should have been.

On another math impossibility note I was dealt BJ in spanish 21 at 32red today 4 times in a row. At least the impossible was in my favor. I love that game and its too bad more dont offer it, I guess not enough house edge.
 

ftg

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I don't know why. but I continue to have very very bad results playing MG's BJ.

Just finished a session of 32 hands.

lost 22 hands
win 7 hands
push 3 hands.

I lost the last 16 hands in a row until my bankroll went to zero, no push in between. about -2.4 SD. Not very bad indeed compared to my previous result.

And yesterday in 80 hands down 30 units. -3.0 SD Max lossing streak is 10 no push in between.
 
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Vesuvio

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ftg said:
I don't know why. but I continue to have very very bad results playing MG's BJ.

Just finished a session of 32 hands.

lost 22 hands
win 7 hands
push 3 hands.

I lost the last 16 hands in a row until my bankroll went to zero, no push in between. about -2.4 SD. Not very bad indeed compared to my previous result.

And yesterday in 80 hands down 30 units. -2.5 SD Max lossing streak is 10 no push in between.
That sort of streak's very common at MG casinos - presumably it's not really random but as with other on-line casino software it's almost impossible to prove. At MG at least you seem to get comparable winning streaks and it evens out in the long run. Best to autoplay to the lowest possible stake and leave it to play in the background to avoid unnecessary stress :D What they want is for you to play a negative progression or chase losses in which case the streakiness will usually make very short work of your deposit.
 

Clayman

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pokeraddict said:
On another math impossibility note I was dealt BJ in spanish 21 at 32red today 4 times in a row. At least the impossible was in my favor. I love that game and its too bad more dont offer it, I guess not enough house edge.
Even more remarkable in that one gets BJ maybe once every 23.5 to 24 hands in Span 21. It is alot nicer when the impossibility is on your side. :)

I like to play Span 21 in B&M casinos due to the lower house edge and the fun of extra pay-offs. Last trip I had 2 7 of spades vs a dealer 7 for the possible $5000 super-bonus. It was fun til the 5 of spades came out. :(

What is the HA of Span 21 where you play?
 

GrandMaster

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Clayman said:
GM - I'm getting higher chances of player 20 than you - what prob are you using? (I'm using .01134 for A,9 & .08911 for 10,10 for 6D from a table.)
I agree with you on the probability of A,9, but I get 0.09399 for the probability of getting two 10 value cards.
 

DrNo888

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I did the Aztec Riches sign up bonus $100 for $100. Did 50 cents autoplay BJ in bonus account. Busted before it even got close to the 20x WR. Did the real account and same thing happened! :eek2:

I am kinda scare of MG BJ now!
 

Clayman

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GrandMaster said:
I agree with you on the probability of A,9, but I get 0.09399 for the probability of getting two 10 value cards.
Thanks - the table was for playable hands so it did not include player hands vs dealer BJ.
 

Clayman

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DrNo888 said:
I did the Aztec Riches sign up bonus $100 for $100. Did 50 cents autoplay BJ in bonus account. Busted before it even got close to the 20x WR. Did the real account and same thing happened! :eek2:
Seems a bit unusual you could lose 2 200-unit bankrolls consecutively in 3600+ hands or less in each account of wagering. I'd think your risk of ruin would be less than 1% in each case. Way less with fewer hands.

Did you change the auto-play table appropriately?

How many hands did you actually play on each account?
 

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