Find the arithmetic mean and the standard deviation of each frequency distribution.
Class Limit Frequency
1-5 2
5-9 8
9-13 15
13-17 6
17-21 38
21-25 31
25-29 13
29-33 7
I managed to find the arithmetic mean doing 2320/120 giving me 19.33
But the standard deviation is giving me trouble
I know the formula is (x-mean)^2 times F
and I did that for example (3-19.33)^2=531.8 (3 being the class mark)
I did that for all them and added them up to get 5040
Then I did stat dev= square root (5040/100) and I get 7.0009 but checking my answer apparently it is wrong.
Is there any way I can do this with a calculator?