Twenty percent of the students in a class of 400 are planning to go to graduate school. The standard deviation of this binomial distribution is
A) 20.
B) 64.
C) 8.
D) 40.

Question

Quizplus · Accepted Answer

The standard deviation of a binomial distribution is given by the formula sqrt(np(1-p)), where n = sample size, p = probability of success for each trial. Here, n = 400 and p = 0.2 (since 20% of the students are planning to go to graduate school).

Plugging in the values, we get: 
sqrt(400*0.2*0.8) = sqrt(64) = 8

Therefore, the standard deviation of this binomial distribution is 8, which corresponds to choice (C).

Twenty Percent of the Students in a Class of 400