# probability outcomes about coin flips

• Sep 30th 2010, 05:54 PM
turtle27
Here's my homework question:

A woman flips a coin exactly 6 times in a row. What is the probability that the coin turned heads up exactly 3 times.

Can you show me as much work as you can and explain the steps to me?

Thank you.
• Sep 30th 2010, 06:07 PM
Gusbob
What have you learned about probability so far? Have you learned about binomial distribution?
• Sep 30th 2010, 06:21 PM
turtle27
Yes, we have discussed binomial distribution.
• Sep 30th 2010, 06:56 PM
Gusbob
Then you would know that:

The number of the particular outcome (3 heads) is
$^nC_k p^k (1-p)^k$

p is the probability of getting heads on 1 flip, so it's 0.5
k is the number of times p will occur, so it's 3
n is the number of times you repeat the process, so it's 6.

This gives you the number of ways 3 heads can be obtained from 6 coin flips.

Now you will need to divide this number by the number of total different outcomes to find the probability.