Thamptondmd
Thamptondmd
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January 15th, 2022 at 5:59:39 AM permalink
What is the formula for calculating the chances of rolling a certain number of 12s before a 7? Say 4 12s before rolling a 7. Assuming 2 die in craps.
Wizard
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Thamptondmd
January 15th, 2022 at 6:42:06 AM permalink
The probability of exactly n 12's before a 7 is (1/7)^n*(6/7). Here is a table for n=0 to 1.

12's Probability
0 0.857142857
1 0.122448980
2 0.017492711
3 0.002498959
4 0.000356994
5 0.000050999
6 0.000007286
7 0.000001041
8 0.000000149
9 0.000000021
10 0.000000003
Last edited by: Wizard on Jan 16, 2022
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ThatDonGuy
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January 15th, 2022 at 7:34:35 AM permalink
Quote: Wizard

The probability of n 12's before a 7 is (6/7)^n*(6/7).


Er, I think you mean (1/7)^n * 6/7.

Also note that this is the probability of rolling exactly n 12s before a 7.

The probability of "rolling n 12s before a 7" is (1/7)^n, which is also 1 / 7^n.
Thamptondmd
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January 15th, 2022 at 9:24:15 AM permalink
Yes, I didnt specify but I do not mean n 12s in a row. Just any chance of rolling n 12s before the seven out.
Thamptondmd
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January 15th, 2022 at 9:28:29 AM permalink
So would the formula (1/7)^n or (1/7)^n * 6/7?
ThatDonGuy
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Thamptondmd
January 15th, 2022 at 9:43:49 AM permalink
Quote: Thamptondmd

So would the formula (1/7)^n or (1/7)^n * 6/7?
link to original post


Again, it depends on whether you mean "exactly" n 12s, and then a 7 before rolling another 12, or not.

If it has to be exact: (1/7)^n * 6/7

If it's just "which will happen first: rolling n 12s, or one 7?", it is (1/7)^n.
DeMango
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January 15th, 2022 at 10:18:42 AM permalink
While we are at it, forgive me if this was posted before, but can we have a column for 18 yos before the seven?
When a rock is thrown into a pack of dogs, the one that yells the loudest is the one who got hit.
Dieter
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January 15th, 2022 at 10:40:59 AM permalink
Quote: DeMango

While we are at it, forgive me if this was posted before, but can we have a column for 18 yos before the seven?
link to original post



(sigh)


I'm supposed to add an obligatory joke, under the thumbtack rules.

A bass player in a local band was having trouble deciding what to dress as for a costume party.
His girlfriend grabbed two drum sticks, tucked them in his pocket, and said "There, now you can go as a musician."
May the cards fall in your favor.
DeMango
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January 15th, 2022 at 12:16:54 PM permalink
Nice to know odds at the crapless table. 18 yo's don't need to be in a row, just before the 7.
When a rock is thrown into a pack of dogs, the one that yells the loudest is the one who got hit.
ThatDonGuy
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January 15th, 2022 at 12:36:02 PM permalink
Quote: DeMango

Nice to know odds at the crapless table. 18 yo's don't need to be in a row, just before the 7.


Seriously? (1/4)^18, which is 1 / 68,719,476,736.

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