# Homework Question

#### jillianleab

##### New Member
Hi everyone:

I'm working on a homework assignment and I am having some trouble with one of the questions. I just don't know which formula to use! Here it is:

In one town, 79% of adults have health insurance. What is the probability that 7 adults selected at random from the town all have health insurance?
A: 0.192
B: 5.53
C: 0.089
D: 0.79

I know the answer is not B, since a probability must be between 0 - 1. I thought maybe it was D, but then that just seems to obvious. I can't find an example similar to this in my text.

I thought maybe I should use the complement rule; A, 7 have insurance, A-bar, none have insurance; but realized that's wrong because it's not asking "at least one" it's asking all. I tried using an online statistics calculator where I input my population size and sample set, but came out with an answer that doesn't appear as an option.

I know this site isn't designed to do my homework for me, but if someone could just point me in the right direction, I'd really appreciate it.

Thanks!

PS: If the answer is D, I'm going to feel like a real idiot!

#### claire9

##### New Member
Hi,
I'm not that brilliant at statistics but here are my thoughts!

If there is 79% of the population that have health insurance and you have chosen 7 people then the probability that they have health insurance is 7/79 which equals 0.089 which is answer C.

#### Akavall

##### New Member
Why not A?

(.79)^7 = 0.192

Therefore the answer is A. This works for all 7 people. If it asked for at least one, the answer would be very close to 1.