mcavanaugh8
mcavanaugh8
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February 23rd, 2018 at 6:25:53 AM permalink
Hey all! I'm not all that math-inclined, so I was just curious as to what the odds are (if this is even possible to calculate) of NOT being dealt a blackjack in a shoe? And how that extrapolates over multiple shoes? I ask because this past weekend I played roughly 10 shoes in 6D blackjack and was not dealt a single blackjack. The guy three seats over from me was dealt, I kid you not, 8 blackjacks in a single shoe. Should have sat there instead!
weezrDASvegas
weezrDASvegas
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February 23rd, 2018 at 9:04:18 AM permalink
I think you askin the complementary probability for getting a blackjack
q = 1 – p

Probability to get blackjack p ~ 5%
Probability to NOT get blackjack: q=1-5%=95% (95% of all hands you deal to yourself).

One site analyzes probably all possible situations – number of decks, number of players, cards remaining in the deck. It goes like this (urls not permitted here)
forums . / blackjack-natural-odds-probability . html
(remove spaced surrounding / .)

You can google also odds to get a blackjack.

Player with 8 blackjacks in a 6D shoe seems unreal. If it was the dealer I would have suspected the automatic shuffler.
mcavanaugh8
mcavanaugh8
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February 23rd, 2018 at 9:31:21 AM permalink
Quote: weezrDASvegas

I think you askin the complementary probability for getting a blackjack
q = 1 – p

Probability to get blackjack p ~ 5%
Probability to NOT get blackjack: q=1-5%=95% (95% of all hands you deal to yourself).

One site analyzes probably all possible situations – number of decks, number of players, cards remaining in the deck. It goes like this (urls not permitted here)
forums . / blackjack-natural-odds-probability . html
(remove spaced surrounding / .)

You can google also odds to get a blackjack.

Player with 8 blackjacks in a 6D shoe seems unreal. If it was the dealer I would have suspected the automatic shuffler.



Hmm, so do you mean it's a 95% chance when being dealt a hand that it will not be a natural blackjack? That seems to make sense. But if it's 95% per hand that you won't get one, my real question is that if you play through 10 shoes and you have a 5% chance of getting blackjack on a hand, what are the chances that never occurs? I don't think I'd ever gone ~3 shoes without one before this weekend! Haha.

And yeah, it was crazy! He had four in a row at one point... the dealer was flabbergasted.

Unfortunately on the next shoe the dealer had three in a row, sandwiched between a couple of 20s and 21s. Was not a good day for me!
gordonm888
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gordonm888
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February 23rd, 2018 at 10:37:17 AM permalink
the answer to your question depends upon the number of hands you can expect to be dealt in 6 shoes, which in turn depends upon the number of players at the table (you have already indicated there was at least one other player.)

So: How many players were at the table?
So many better men, a few of them friends, are dead. And a thousand thousand slimy things live on, and so do I.
weezrDASvegas
weezrDASvegas
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February 23rd, 2018 at 10:38:28 AM permalink
Quote: mcavanaugh8

Hmm, so do you mean it's a 95% chance when being dealt a hand that it will not be a natural blackjack? That seems to make sense. But if it's 95% per hand that you won't get one, my real question is that if you play through 10 shoes and you have a 5% chance of getting blackjack on a hand, what are the chances that never occurs? I don't think I'd ever gone ~3 shoes without one before this weekend! Haha.

And yeah, it was crazy! He had four in a row at one point... the dealer was flabbergasted.

Unfortunately on the next shoe the dealer had three in a row, sandwiched between a couple of 20s and 21s. Was not a good day for me! forums . / saliu . com / blackjack-natural-odds-probability . html



You described a phishy session in that casino. Automatic or continuous shufflers in “beast mode” maybe?

NOT a blackjack in 6D is the opposite of 1 bj in 6D. The site I pointed you to was not printed correctly here because of no urls allowed policy. It has the formulas for many situations. Number of players is very important also. Number of bjs per deck should be distributed equally amongst all players. Like every player should get 2 bjs on average per deck if plying some 10 decks.

I don’t trust those automatic shufflers for the life of me. But they are part of life now.
weezrDASvegas
weezrDASvegas
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February 23rd, 2018 at 11:02:59 AM permalink
The probability of getting a blackjack is a hypothetical situation looks like. You shuffle a deck and deal 2 cards. If you do it 100 times, the 2-card hand is a bj in 5 situations; in other 95 shuffles the hand is not a blackjack.

But there is the dealer also. So you get the bj every 21 cards and so does the dealer. That should be also the case with dealer plus 5 players in a 6D shoe. Of course the cards are not perfectly distributed. In one 6D shuffle you might get 8 bjs while the dealer gets one or none—and vice versa. That is very rare if the game is fair. It’s hard to believe you got NO bj in 10 6D shuffles even considering penetration. I never remember something similar happening to me.
BlackjackGuy123
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February 23rd, 2018 at 11:14:04 AM permalink
Depends, how many players are playing?

If it is just heads up and we are talking about a shoe where there is 1 decks cut off out of six, then we can expect to get 52 rounds in playing heads up. So the odds of not getting blackjack in one trial is 95.17%.

.9517 to the 52nd power is 7.6%


But at a crowded table the probability would be much higher.
mcavanaugh8
mcavanaugh8
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February 23rd, 2018 at 1:10:54 PM permalink
Quote: gordonm888

the answer to your question depends upon the number of hands you can expect to be dealt in 6 shoes, which in turn depends upon the number of players at the table (you have already indicated there was at least one other player.)

So: How many players were at the table?



It was a full table--maybe a hand or two lag between a player getting up and another sitting down, but it was almost always full for the shoes I was in.
mcavanaugh8
mcavanaugh8
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February 23rd, 2018 at 1:12:00 PM permalink
Quote: BlackjackGuy123

Depends, how many players are playing?

If it is just heads up and we are talking about a shoe where there is 1 decks cut off out of six, then we can expect to get 52 rounds in playing heads up. So the odds of not getting blackjack in one trial is 95.17%.

.9517 to the 52nd power is 7.6%


But at a crowded table the probability would be much higher.




Full table in 6D BJ with about 2 decks penetration on average.

Hmm interesting. Maybe not as uncommon as I thought, then.
mcavanaugh8
mcavanaugh8
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February 23rd, 2018 at 1:13:58 PM permalink
Quote: weezrDASvegas

The probability of getting a blackjack is a hypothetical situation looks like. You shuffle a deck and deal 2 cards. If you do it 100 times, the 2-card hand is a bj in 5 situations; in other 95 shuffles the hand is not a blackjack.

But there is the dealer also. So you get the bj every 21 cards and so does the dealer. That should be also the case with dealer plus 5 players in a 6D shoe. Of course the cards are not perfectly distributed. In one 6D shuffle you might get 8 bjs while the dealer gets one or none—and vice versa. That is very rare if the game is fair. It’s hard to believe you got NO bj in 10 6D shuffles even considering penetration. I never remember something similar happening to me.



Variance was not on my side, it seems. I was honestly baffled--I was dealt PLENTY of tens and aces. I can't even remember how many soft hands I doubled on against dealer low cards. I just never got the ten and ace together lol.
weezrDASvegas
weezrDASvegas
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February 26th, 2018 at 3:58:01 PM permalink
Quote: BlackjackGuy123

Depends, how many players are playing?

If it is just heads up and we are talking about a shoe where there is 1 decks cut off out of six, then we can expect to get 52 rounds in playing heads up. So the odds of not getting blackjack in one trial is 95.17%.

.9517 to the 52nd power is 7.6%


But at a crowded table the probability would be much higher.



On the other hand, getting at least one blackjack in 52 rounds –
“The probability of at least one success in 52 trials for an event of probability p=0.0483 is 92.38% or 1 in 1.08.” (courtesy of SuperFormula.exe).

The chance in a complete 6D shoe is overwhelmingly in favor of at least one blackjack (better than 10 to 1). Playing through 10 shoes as mcavanaugh8 did is overwhelmingly highly favorable to at least one blackjack. That is 520 trials!!!

“The probability of at least one success in 520 trials for an even of probability p=0.0483 is 0.9999999999.”

Its like tossing the coin 5000 times to get b0th heads/tails at least once. mcavanaugh8 didn’t get that virtually certain outcome!!! I BLAME the automatic shufflers… again… and again… 520 times!

Ok this is for heads-up play. The probability you get a blackjack is very high even with 7 players at the table and plying 10 shoes.
gordonm888
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gordonm888
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February 26th, 2018 at 6:09:54 PM permalink
"52 trials in a 6 deck shoe" assumes 100% penetration and one on one play.

With 4 decks dealt per shoe and a full table (7 players) I think there would be about 9-10 hands dealt per shoe. So ten shoes would be roughly 100 hands. Odd s of not getting at least one blackjack in ten shoes would be on the order of 0.035% -approximately 1 in 3,000.
So many better men, a few of them friends, are dead. And a thousand thousand slimy things live on, and so do I.
Lucca3927
Lucca3927
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February 26th, 2018 at 7:38:53 PM permalink
I find that the odds of not getting it grows exponentially when you're down to your last bet.
"I should have bet black." - Winston Churchill .
weezrDASvegas
weezrDASvegas
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February 27th, 2018 at 8:37:27 AM permalink
@gordonm888
Your penetration is 66%. So if you play through 10 6D shoes a day it takes 3000 days to be in a no blackjack situation. That would be 8 years of daily play and in one of those days you wont hit a blackjack.
weezrDASvegas
weezrDASvegas
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February 27th, 2018 at 8:38:04 AM permalink
“I find that the odds of not getting it grows exponentially when you're down to your last bet.”

Sarcastic but just about every player says it’s true.
mustangsally
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February 27th, 2018 at 9:39:03 AM permalink
Quote: weezrDASvegas

On the other hand, getting at least one blackjack in 52 rounds –
“The probability of at least one success in 52 trials for an event of probability p=0.0483 is 92.38% or 1 in 1.08.” (courtesy of SuperFormula.exe).

agree
about 12 out of 13 in 52 rounds
round Xprob NO BJ1 inprob at least 1 BJ1 inout of
10.95171.0510.048320.704.
20.905732891.1040.0942671110.608.
30.8619859911.1600.1380140097.246.
40.8203520681.2190.1796479325.566.
50.7807290631.2810.2192709374.561.
60.7430198491.3460.2569801513.891.
70.7071319911.4140.2928680093.415.
80.6729775161.4860.3270224843.058.
90.6404727021.5610.3595272982.781.
100.609537871.6410.390462132.561.
110.5800971911.7240.4199028092.382.
120.5520784971.8110.4479215032.233.
130.5254131051.9030.4745868952.107.
140.5000356522.0000.4999643482.000.
150.475883932.1010.524116071.9081.1 out of 2.1
160.4528987362.2080.5471012641.8281.21 out of 2.21
170.4310237272.3200.5689762731.7581.32 out of 2.32
180.4102052812.4380.5897947191.6961.44 out of 2.44
190.3903923662.5620.6096076341.6401.56 out of 2.56
200.3715364152.6920.6284635851.5911.69 out of 2.69
210.3535912062.8280.6464087941.5471.83 out of 2.83
220.3365127512.9720.6634872491.5071.97 out of 2.97
230.3202591853.1220.6797408151.4712.12 out of 3.12
240.3047906663.2810.6952093341.4382.28 out of 3.28
250.2900692773.4470.7099307231.4092.45 out of 3.45
260.2760589313.6220.7239410691.3812.62 out of 3.62
270.2627252853.8060.7372747151.3562.81 out of 3.81
280.2500356533.9990.7499643471.3333 out of 4
290.2379589314.2020.7620410691.3123.2 out of 4.2
300.2264655154.4160.7735344851.2933.42 out of 4.42
310.2155272314.6400.7844727691.2753.64 out of 4.64
320.2051172654.8750.7948827351.2583.88 out of 4.88
330.1952101025.1230.8047898981.2434.12 out of 5.12
340.1857814545.3830.8142185461.2284.38 out of 5.38
350.1768082095.6560.8231917911.2154.66 out of 5.66
360.1682683735.9430.8317316271.2024.94 out of 5.94
370.160141016.2440.839858991.1915.24 out of 6.24
380.15240626.5610.84759381.1805.56 out of 6.56
390.145044986.8940.854955021.1705.89 out of 6.89
400.1380393087.2440.8619606921.1606.24 out of 7.24
410.1313720097.6120.8686279911.1516.61 out of 7.61
420.1250267417.9980.8749732591.1437 out of 8
430.1189879498.4040.8810120511.1357.4 out of 8.4
440.1132408328.8310.8867591681.1287.83 out of 8.83
450.1077712999.2790.8922287011.1218.28 out of 9.28
460.1025659469.7500.8974340541.1148.75 out of 9.75
470.0976120110.2450.902387991.1089.24 out of 10.24
480.0928973510.7650.907102651.1029.76 out of 10.76
490.08841040811.3110.9115895921.09710.31 out of 11.31
500.08414018611.8850.9158598141.09210.88 out of 11.88
510.08007621512.4880.9199237851.08711.49 out of 12.49
520.07620853313.1220.9237914671.08212.12 out of 13.12
530.07252766113.7880.9274723391.07812.79 out of 13.79
540.06902457514.4880.9309754251.07413.49 out of 14.49
550.06569068815.2230.9343093121.07014.22 out of 15.22
560.06251782815.9950.9374821721.06715 out of 16
570.05949821716.8070.9405017831.06315.81 out of 16.81
580.05662445317.6600.9433755471.06016.66 out of 17.66
590.05388949218.5560.9461105081.05717.56 out of 18.56
600.0512866319.4980.948713371.05418.5 out of 19.5
610.04880948520.4880.9511905151.05119.49 out of 20.49
620.04645198721.5280.9535480131.04920.53 out of 21.53
630.04420835622.6200.9557916441.04621.62 out of 22.62
640.04207309323.7680.9579269071.04422.77 out of 23.77
650.04004096224.9740.9599590381.04223.97 out of 24.97
660.03810698426.2420.9618930161.04025.24 out of 26.24
670.03626641627.5740.9637335841.03826.57 out of 27.57
680.03451474928.9730.9654852511.03627.97 out of 28.97
690.03284768630.4440.9671523141.03429.44 out of 30.44
700.03126114331.9890.9687388571.03230.99 out of 31.99
710.0297512333.6120.970248771.03132.61 out of 33.61
720.02831424535.3180.9716857551.02934.32 out of 35.32
730.02694666737.1100.9730533331.02836.11 out of 37.11
740.02564514338.9940.9743548571.02637.99 out of 38.99
750.02440648340.9730.9755935171.02539.97 out of 40.97
760.0232276543.0520.976772351.02442.05 out of 43.05
770.02210575445.2370.9778942461.02344.24 out of 45.24
780.02103804647.5330.9789619541.02146.53 out of 47.53
790.02002190949.9450.9799780911.02048.95 out of 49.95
800.0190548552.4800.980945151.01951.48 out of 52.48
810.01813450155.1440.9818654991.01854.14 out of 55.14
820.01725860557.9420.9827413951.01856.94 out of 57.94
830.01642501460.8830.9835749861.01759.88 out of 60.88
840.01563168663.9730.9843683141.01662.97 out of 63.97
850.01487667667.2190.9851233241.01566.22 out of 67.22
860.01415813270.6310.9858418681.01469.63 out of 70.63
870.01347429474.2150.9865257061.01473.22 out of 74.22
880.01282348677.9820.9871765141.01376.98 out of 77.98
890.01220411281.9400.9877958881.01280.94 out of 81.94
900.01161465386.0980.9883853471.01285.1 out of 86.1
910.01105366590.4680.9889463351.01189.47 out of 90.47
920.01051977395.0590.9894802271.01194.06 out of 95.06
930.01001166899.8830.9899883321.01098.88 out of 99.88
940.009528105104.9530.9904718951.010103.95 out of 104.95
950.009067897110.2790.9909321031.009109.28 out of 110.28
960.008629918115.8760.9913700821.009114.88 out of 115.88
970.008213093121.7570.9917869071.008120.76 out of 121.76
980.0078164127.9360.99218361.008126.94 out of 127.94
990.007438868134.4290.9925611321.007133.43 out of 134.43
1000.007079571141.2520.9929204291.007140.25 out of 141.25


the median looks to be at
14 rounds of play
Now, that seems too low by my lifetime of play

of course
over a lifetime of BJ play one can get close to the expectation

over a weekend of play
0 Bjs happens to many

enjoy the journey
enjoy the ride
Sally
I Heart Vi Hart
mcavanaugh8
mcavanaugh8
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February 27th, 2018 at 10:29:25 AM permalink
This is all fascinating--thanks to everyone who's punching the numbers! Apparently it was even more improbable than I thought. I guess this means I'm due for a big win, right?! ;)
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