The Excel file labeled Customer service champs.xlsx lists the top 25 companies, with the best customer service scores ranked by Business Week in 2012.

a. Determine the coefficient of variation.

b. Calculate the z-score for a company with a score of 900.

c. Test if the empirical rule holds true by determining the percentage of observations that fall within { two standard deviations from the mean.

d. Verify that Chebyshev’s Theorem holds true by determining the percentage of observations that fall within

{ three standard deviations from the mean.

AppendixLO1