1. The number of minutes that a sample of students in a history class spent on an exam is given. {83, 52, 47, 76, 80, 91, 47, 21, 36, 52, 51, 64, 78, 62, 53, 49}. Find the following statistics. You may use your calculator as appropriate.

a. the variance of the sample.

b. the range of the sample.

c. the coefficient of variation of the sample.

d. the z-score corresponding to 60 minutes.

e. 20 , the 20 th percentile.

2. Use a formula to calculate the standard deviation of the sample {1, 3, 9}.