A manufacturer who is considering the implementation of a one-week training program for all new employees decides to test the program with the next

A manufacturer who is considering the implementation of a one-week training program for all new employees decides to test the program with the next 100 employees hired, and then compare their productivity rate to the productivity rate of new employees based on past records—a rate that is normally distributed with a mean of 60 and a standard deviation of 8. The new program needs to produce a minimum improvement of 4 to be considered worthwhile.

What is the comparison distribution's standard deviation?