Calculating the Mean and Standard Deviation of Grouped Data

Consider the frequency table of the number of runs scored by the 1996 New York Yankees.

Number of Runs Scored Class Mark
or Class Midpoint		 Frequency
0 - 15 7.5 7
16 - 31 23.5 5
32 - 47 39.5 2
48 - 63 55.5 3
64 - 79 71.5 0
80 - 95 87.5 4
96 - 111 103.5 2

Determine the mean and the standard deviation for the number of runs scored per 1996 New York Yankee. NOTE: Class Marks are also called Class Midpoints.