May 24, 2015

Homework Help: Did i do this right??? STATS

Posted by Jen on Wednesday, October 26, 2011 at 6:19pm.

3. In testing a new drug, researchers found that 10% of all patients using it will have a mild side effect. A random sample of 14 patients using the drug is selected. Find the probability that:

(A) exactly two will have this mild side effect
(B) at least three will have this mild side effect.

I got this for (A):
= 14!/(14-2)!2! (0.10)(0.90)14-2^2
= 14*13*12!/12!2*1(0.10)(0.90)12^2
= 14*13/2*1(0.01)(0.28)
= 182/2(0.01)(0.28)
= 91(0.01)(0.28) = 0.25 or 25%

But i'm not sure how to do (B)

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