stats question

Find the standard deviation, s, of sample data summarized in the frequency distribution table given 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, 9.0. S= " [ E (F . x 2 ) ] - [[ ( . x ) ] n(n - 1) Interval 20-29 30-39 40-49 50-59 60-69 70-79 Frequency co 35 25 Standard deviation = (Round to one decimal place as needed.)