# Binomial Probability

• Mar 5th 2011, 01:18 PM
GDK76
Binomial Probability
Hello everyone,

"In the game of craps you roll two 6-sided dice. A sum of 2, 11, or 12 is considered a failure while all others are considered a success. Find the probability of rolling exactly 5 successes in 13 rolls."

I tried setting up the values for the formula nCx*P^x*Q^n-x but however, I am stuck finding the value of p which is probability of success. At first i got 8/11 but i am not certain if that is right or not.
• Mar 5th 2011, 01:22 PM
mr fantastic
Quote:

Originally Posted by GDK76
Hello everyone,

"In the game of craps you roll two 6-sided dice. A sum of 2, 11, or 12 is considered a failure while all others are considered a success. Find the probability of rolling exactly 5 successes in 13 rolls."

I tried setting up the values for the formula nCx*P^x*Q^n-x but however, I am stuck finding the value of p which is probability of success. At first i got 8/11 but i am not certain if that is right or not.

1 - p = (number of ways of getting 2, 11 or 12)/36. Using a dice table might help: Dice table
• Mar 5th 2011, 01:27 PM
Plato
Quote:

Originally Posted by GDK76
"In the game of craps you roll two 6-sided dice. A sum of 2, 11, or 12 is considered a failure while all others are considered a success. Find the probability of rolling exactly 5 successes in 13 rolls."

In one roll $\displaystyle \mathif{P}(2\cup 11\cup 12)=\frac{1}{9}$.
So the probability of success is $\displaystyle \frac{8}{9}$.
Now apply the binomial formula.