In a batch of 100 cell phones, there are, on average, 5 defective ones. If a random sample of 30 is selected, find the probability of 2 defective ones.
A) 0.0500
B) 0.3000
C) 0.3163
D) 0.0667

Question

Quizplus · Accepted Answer

This is a binomial distribution problem with n=30, p=0.05 (probability of a defective phone), and we want to find the probability of 2 defective ones. Using the binomial probability formula, we get:

P(X=2) = (30 choose 2) (0.05)^2 (1-0.05)^28
P(X=2) = 435 (0.0025) (0.9464)
P(X=2) = 0.3163

Therefore, the probability of 2 defective phones is 0.3163 or approximately 0.32. So, the best choice is C.

In a Batch of 100 Cell Phones, There Are, on Average