mikjd203
Joined: Feb 3, 2018
• Posts: 2
February 3rd, 2018 at 6:14:34 AM permalink
Does anyone know what the odds are of losing 17 out of 20 hands( 11 in a row ) in blackjack playing perfect basic strategy. happened to me the other day on a shufflemaster hybrid game. Day before I left a big winner.
OnceDear
Joined: Jun 1, 2014
• Posts: 4623
February 3rd, 2018 at 7:23:27 AM permalink
Quote: mikjd203

Does anyone know what the odds are of losing 17 out of 20 hands( 11 in a row ) in blackjack playing perfect basic strategy. happened to me the other day on a shufflemaster hybrid game. Day before I left a big winner.

Without enumerating it? Pretty much guaranteed to happen to you, especially if you play more than 20 games per lifetime.

Or, very rough and ready estimate if we ignore pushes and just consider the odds of losing a hand at a generous 50%, in which case the odds of losing your first 11 hands is 0.5*11 = 1 in 2048.
Sorry, cant yet be bothered to answer the full question except to say that the probability that it did happen to you is approaching 100%
Take care out there. Spare a thought for the newly poor who were happy in their world just a few days ago, but whose whole way of life just collapsed..
mustangsally
Joined: Mar 29, 2011
• Posts: 2463
February 3rd, 2018 at 7:59:39 AM permalink
Quote: mikjd203

Does anyone know what the odds are of losing 17 out of 20 hands( 11 in a row ) in blackjack

you just asked 2 questions in 1.
I thought I was the only one that did that a a lot (I still might be)
***** ***** *
Q1)what the odds are of losing 17 out of 20 hands in blackjack
Q2) given I lost 17 out of 20 hands, what is the probability I lost 11 in a row

Q1
I say 17 lost and the other 3 won?
or 2 wins,1tie
so we do not know...
we also do not know IF any splits or double down bets were made and lost.

less accurate method:
p(lose)=0.4788 (about - depends on game rules)
using Excel =BINOMDIST(17,20,0.4788,0)
result
0.000589574
about 1 in 1,696 sets of 20 hands

more accurate method:
http://stattrek.com/online-calculator/multinomial.aspx

Win 43.34%
Loss 47.88%
Tie 8.78%

0.00034
about 1 in 2,941 sets of 20 hands
***********
Q2) given I lost 17 out of 20 hands, what is the probability I lost 11 in a row

a different type of a question
*****before one plays the next 20 hands
it would be around (not counting Ties)
parameter p(lose)=0.5249

result: 0.004396821712930
about 1 in 227 sets of 20 hands
******
before one plays the next 20 hands
it would be around (Counting Ties)

result: 0.003700473
about 1 in 270 sets of 20 hands
done in Excel (transition matrix and recursion)
***********
but we KNOW you lost 17 hands
so the probability should be different.
(we can use combinations for this one)

bottom lines:
losing playing Blackjack is a given (so are losing streaks)
even playing perfectly
and the more one plays
it can be heard
"NOW!! I have SEEN IT ALL!"

and that is not really a true statement. keep on playing!
Sally
I Heart Vi Hart
mikjd203
Joined: Feb 3, 2018
• Posts: 2
February 3rd, 2018 at 8:10:00 AM permalink
Guess I was a little vague. I dont have the exact number of pushes or the splits and double downs. Guess that would have made your predictions more accurate. All in all, seems like its fairly rare for that to happen given your equations. Ive played blackjack a long, long time and have never had that happen before. almost seems like manipulation. although I dont know how many times(so irrelevant but for the story) lost many hands with dealer showing weak hands of 5 or 6. We all know that happens, but again not to this frequency. Guess you can chalk it up to horrible, horrible luck. Get 'em next time!
mustangsally
Joined: Mar 29, 2011
• Posts: 2463
February 3rd, 2018 at 8:16:30 AM permalink
Quote: OnceDear

just consider the odds of losing a hand at a generous 50%, in which case the odds of losing your first 11 hands is 0.5*11 = 1 in 2048.

say a fair coin flip
a TAILs losing streak of at least 11 in 20 trials would then be about
0.002685546875000 or
1 in 372 sets of 20

not very high for just 1 attempt

but 'super way easier' (new math term) with way more attempts

Sally
I Heart Vi Hart
mustangsally
Joined: Mar 29, 2011
• Posts: 2463
February 3rd, 2018 at 8:27:20 AM permalink
Quote: mikjd203

All in all, seems like its fairly rare for that to happen given your equations.

it is only
'fairly rare' when you play only 20 lifetime hands as pointed out before.

you play for a long time
and look at all the 20 hand sets played

it has now a very high probability of happening
at least 1 time (and it just did)

Sally
I Heart Vi Hart