In a sample of 20 hand-held calculators,15 are known to be nonfunctional.If 7 of these calculators are selected at random,what is the probability that exactly 5 in the selection are nonfunctional? Round to the nearest thousandth.
A)0
B)0.714
C)0.387
D)0.467
E)0.750

Question

Quizplus · Accepted Answer

We can use the binomial probability formula to solve this problem:
P(X=5) = (15 choose 5) * (5 choose 2) / (20 choose 7) = 3003 * 10 / 77520 = 0.387 (rounded to the nearest thousandth)

In a Sample of 20 Hand-Held Calculators,15 Are Known to Be