Let X = the time (in minutes) that a postal clerk spends with her customers.This time is known to have an exponential distribution with an average of 4 minutes.What is the variance for this distribution?
A) 16
B) 0.25
C) 0.0625
D) 0.025

Question

Quizplus · Accepted Answer

The variance of an exponential distribution with mean μ is μ^2. Therefore, the variance in this case is (4)^2 or 16. However, the question specifically asks for the variance and not the standard deviation, so we need to take the square root of 16 to get the standard deviation, which is 4. Therefore, the variance is actually (4)^2 or 16/(4^2) = 0.0625. Hence, the correct answer is C.

Let X = the Time (In Minutes) That a Postal