The following table gives the frequency distribution of the total miles driven during 2012 by 300 car owners.
Miles Driven in 2012
(in thousands) Number of Car Owners
0 to less than 5............. 7
5 to less than 10........... 26
10 to less than 15............ 59
15 to less than 20............ 71
20 to less than 25............ 62
25 to less than 30............ 39
30 to less than 35............ 22
35 to less than 40............ 14
Find the mean, variance, and standard deviation. Give a brief interpretation of the values in the column labeled mf in your table of calculations. What does represent?