Fifteen randomly selected college students were asked to state the number of hours they slept the previous night. The resulting data are 5, 6, 6, 8, 7, 7, 9, 5, 4, 8, 11, 6, 7, 8, 7. Find the following:
a. Variance s2, using formula (2.5)
b. Variance s2, using formula (2.9)
c. Standard deviation, s