## anonymous 4 years ago A fair coin is flipped four times. What is the probability of getting heads at least once?

1. anonymous

didn't we just do this?

2. anonymous

no

3. anonymous

oh you are right, 4 times. sorry

4. anonymous

we can list them or we can use a formula. your choice

5. anonymous

a formula

6. anonymous

at least once means 1 or 2 or 3 or 4, so not 0 the probability you get zero heads is $(\frac{1}{2})^4$so the probability you get at least one head is $1-(\frac{1}{2})^4$

7. anonymous

The sample space of the experiment is hhhh hhht hhtt httt hhth hthh htth htht thhh tthh ttth thth thht tttt thtt ttth so the number of times of getting heads at least once is 15 out of 16. But there is a better way. If you know that the probability of getting a heads at least once is mutually exclusive of getting all tails then P[heads at least once] = 1 - P[all tails] = 1 - 1/16 = 15/16

8. anonymous

of course zero heads mean all tails, i.e. you got t t t t

9. anonymous

satellite u r brainy