Probability: Finding n and p.

I am preparing for my finals and came across this question:

I am quite confused on this one since we have two unknowns. I tried using binomials distribution with with n being the number of patients to be vacinated in order to get at least 1000 successes, but i cannot calculate both and from the same equation.

is there any other approach to solve this problem? thank you.

Re: Probability: Finding n and p.

Quote:

Originally Posted by

**chutiya** I am preparing for my finals and came across this question:

I am quite confused on this one since we have two unknowns. I tried using binomials distribution with

with n being the number of patients to be vacinated in order to get at least 1000 successes, but i cannot calculate both

and

from the same equation.

is there any other approach to solve this problem? thank you.

X ~ Binomial(n, p)

Pr(X < 1000) = 0.05

You will now need to use the normal approximation to make further progress.

Re: Probability: Finding n and p.

Thank You. Thats what I was thinking about.

Apparently, the value of p had been missing in the question, which was p=90%(which was the major source of my trouble) and I was supposed to find "n" only. That makes life easy. I just used normal approximation to find n.