Calculate the sample standard deviation and sample variance for the following frequency distribution of final exam scores in a statistics class. If necessary, r

Question

Final Exam Scores
Class Frequency
51 - 60 6
61 - 70 11
71 - 80 6
81 - 90 11
91 - 100 4

Calculate the sample standard deviation and sample variance for the following frequency distribution of final exam scores in a statistics class. If necessary, round to one more decimal place than the largest number of decimal places given in the data

Answer 1

The average is 

(6 x 55.5 + 11 x 65.5 + 6 x 75.5 + 11 x 85.5 + 4 x 95.5)/(6+11+6+11+4) = 2829/38 = 74.44736

 

variance = 6157.895/37 = 166.4295945

std dev=12.9 = sqrt( variance) = sqrt( 166.4295945)