Suppose that 2.4% of people are left handed.If 30 people are selected at random,what is the standard deviation of the number of right-handers in the group?
A)0.70272
B)0.72
C)0.85
D)0.84
E)5.41

Question

Quizplus · Accepted Answer

Let X be the number of right-handers in the group. Then, X follows a binomial distribution with parameters n=30 and p=1-0.024=0.976.

The mean of X is E(X) = np = 30*0.976 = 29.28.

The variance of X is Var(X) = np(1-p) = 30*0.976*(1-0.976) = 0.73408.

The standard deviation of X is the square root of the variance, which is approximately 0.84.

Therefore, the answer is (D) 0.84.

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