Question

The probability that a person has immunity to a particular disease is 0.6. Find the mean number who have

immunity in samples of size 12.

Answer 1

Explanation:

This is a binomial probability problem. There are only two outcomes. It is either a chosen person has immunity to a particular disease or he does not. The probability of success in this case, p is the probability that a chosen person has immunity to a particular disease. Thus

p = 0.6

The probability of failure, q is q = 1 - p

Thus, q = 1 - 0.6 = 0.4

Mean = np

Where n represents sample size. Thus,

Mean = 12 × 0.6 = 7.2