## Elementary Statistics (12th Edition)

By using the values from the picture and the given formula: $s=\sqrt {\frac{n\cdot[\sum(f\cdot x^2)]-[\sum (f\cdot x)^2]}{n\cdot(n-1)}}=\sqrt {\frac{82\cdot 169980.5-3649^2}{82\cdot 81}}=9.69 \ years.$ This value is lower than 3 and more than 1 other data from other exercises, so seems to be good.