The following data represent the quarterly sales tax receipts (in thousands of dollars) submitted to the comptroller of the Route 66 Common Outlets for the period ending March 2014 by all 50 business establishments in that locale:

10.3 11.1 9.6 9 14.5

13 6.7 11 8.4 10.3

13 11.2 7.3 5.3 12.5

8 11.8 8.7 10.6 9.5

11.1 10.2 11.1 9.9 9.8

11.6 15.1 12.5 6.5 7.5

10 12.9 9.2 10 12.8

12.5 9.3 10.4 12.7 10.5

9.3 11.5 10.7 11.6 7.8

10.5 7.6 10.1 8.9 8.6

a. Compute the mean, variance, and standard deviation for this population.

b. What proportion of these businesses have quarterly sales tax receipts within 1, 2, or 3 standard deviations of the mean?

c. Compare and contrast your findings with what would be expected based on the empirical rule. Are you surprised at the results in (b)?