# Math Help - Statistics basic question

1. ## Statistics basic question

Hello people I have this problem to solve.

The probability that a patient recovers from a rare blood disease is 0.6. If 18 people are known to have contracted this disease, what is the probability that:

(i) at least 15 survive?
p=0.6

15/18*0.6=0.5, 50%

(ii) from 5 to 10 survive?

(iii) Exactly 12 survive?

(I have attempted the first part not sure if it is correct. Really appreciate replys in regads to the answer).

2. Use the binomial theorem for these problems,
$P(X=k) = \binom{n}{k}p^k(1-p)^{n-k}$

In your case n = 18 & p= 0.6

a) P(X=15)+P(X=16)+P(X=17)+P(X=18)

b) P(X=5)+P(X=6)+P(X=7)+P(X=8)+P(X=9)+P(X=10)

c) P(X=12)

I don't think your attempt for part a) is very robust.

3. Thanks for your reply pickslides. Yes now I know where to use that x value cheers.