The National Sporting Goods Association (NSGA) conducted a survey of the ages of people that purchased athletic footwear in 2009. The ages are summarized in the following relative frequency distribution. Assume the survey was based on 100 individuals.

Age of Purchaser Percent

Under 14 years old 15

14 to 17 years old 4

18 to 24 years old 6

25 to 34 years old 15

35 to 44 years old 16

45 to 64 years old 28

65 years old and over 16

a.Calculate the average age of this distribution. Use 10 as the midpoint of the first class and 75 as the midpoint of the last class.(Round intermediate calculations to at least 4 decimal places and final answer to 2 decimal places.)

b.Calculate the sample standard deviation.(Round intermediate calculations to at least 4 decimal places and final answer to 2 decimal places.)