(solution) There are 40 students in an elementary statistics class. On the

(solution) There are 40 students in an elementary statistics class. On the

There are 40 students in an elementary statistics

class. On the basis of years of experience, the

instructor knows that the time needed to grade a

randomly chosen first examination paper is a

random variable with an expected value of

6 min and a standard deviation of 6 min.

a. If grading times are independent and the

instructor begins grading at 6:50 p.m. and

grades continuously, what is the (approximate)

probability that he is through grading

before the 11:00 p.m. TV news begins?

b. If the sports report begins at 11:10, what is the

probability that he misses part of the report if

he waits until grading is done before turning

on the TV?