Compute estimated mean of frequency distribution, standard deviation, variance

31. Determine the estimated mean of the following frequency distribution.

Class                 Frequency
0 up to 5            2
5 up to 10          7
10 up to 15        12
15 up to 20         6
20 up to 25         3

94. Compute the range, the standard deviation, and the variance.

A sample of the amounts paid for parking on Saturday at the downtown parking garage in Toronto was organized into the following frequency distribution.

Amount Paid             Frequency
$0.50 up to $0.75       2
0.75 up to   1.00        7
1.00 up to   1.25        15
1.25  up to   1.50       28
1.50  up to    1.75      14
1.75  up to    2.00       9
2.00  up to    2.25       3
2.25  up to     2.50      2