Question: The file Tax contains the quarterly sales tax receipts (in thousands of dollars) submitted to the comptroller of the Village of Fair Lake for the period ending March 2009 by all 50 businesses establishments in that locale:

10.3 11.1 9.6 9.0 14.5

13.0 6.7 11.0 8.4 10.3

13.0 11.2 7.3 5.3 12.5

8.0 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

10.0 12.9 9.2 10.0 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 percentage of these businesses have quarterly sales tax receipts within + 1, + 2, or + 3 standard deviations of the mean?

c. Compare your findings with that would be expected on the basis of the empirical rule. Are you surprised at the results in (b)?