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 16 14 to 17 years old 8 18 to 24 years old 11 25 to 34 years old 12 35 to 44 years old 10 45 to 64 years old 29 65 years old and over 14 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.)