A survey of college students taking the professional exam to be certified as public school teachers shows that 15 percent fail.On a national exam day,12,000 students take the test.Let x denote the number who fail.The mean and standard deviation of the random variable x are,respectively:
A) 1800; 1530
B) 1800; 39.11
C) 10,200; 1530
D) 10,200; 39.11
E) 1200; 35.71

Question

Quizplus · Accepted Answer

The mean of a binomial distribution is np and the standard deviation is sqrt(np(1-p)). Here, n = 12000 and p = 0.15, so the mean is 1800 and the standard deviation is sqrt(1800*0.85) = 39.11.

A Survey of College Students Taking the Professional Exam to Be