Advertising expenses are a significant component of the cost of goods sold. Listed below is a frequency distribution showing the advertising expenditures for 60 manufacturing companies located in the Southwest. Estimate the mean and the standard deviation of advertising expenses.
Advertising Expenditure ($ millions) Number of Companies
25 up to 35............ 5
35 up to 45............ 10
45 up to 55............ 21
55 up to 65............ 16
65 up to 75............ 8
Total.............. 60