Find the standard deviation, s, of sample data summarized in the frequency distribution table below by using the formula below, where x represents the class midpoint, f represents the class frequency, and n represents the total number of sample values. Also, compare the computed standard deviation to the standard deviation obtained from the original list of data values, 11.1.

Interval

20-26
27-33
34-40
41-47
48-54
55-61
62-68
Frequency
1
4
3
1
12
32
33