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. The mean expense is $52.0 million and the standard deviation is $11.32 million. Is it reasonable to conclude the sample data are from a population that follows a normal probability distribution? Use the .05 significance level.
Advertising Expense ($ Million) 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