A study of college dropouts models the number of undergraduate credits a student successfully earns prior to quitting using an exponential random variable.If the observed average number of credits earned is 22.5, what proportion of students drop out with more than 100 credits, assuming an exponential random variable is appropriate here?
A) 0.0117
B) 0.0392
C) 0.9802
D) 0.2250

Question

Quizplus · Accepted Answer

The exponential distribution is defined by its mean, which in this case is 22.5 credits. The probability that a student drops out after earning more than x credits is given by the survival function, which is $e^{-x/\lambda}$, where $\lambda$ is the mean. Plugging in the values, we get $e^{-100/22.5} \approx 0.0117$.

A Study of College Dropouts Models the Number of Undergraduate