A professor would like to test the hypothesis that the average number of minutes that a student needs to complete a statistics exam has a standard deviation that is less than 5.0 minutes. A random sample of 15 students was selected and the sample standard deviation for the time needed to complete the exam was found to be 4.0 minutes. What would be the number of degrees of freedom for this hypothesistest?

A.

13

B.

16

C.

14

D.

15