okay try this...
try to do the computational forumala which says EX2 (sum of x squared) -(EX)2 (sum of x) then squared over N so it should be (since i dont have symbols)
1. make two colums
X and X2
2. list all your X values for column 1, then list all your X values in colum2 squared (so square each x value.) so you should have a list of x scores and al list of squared x scores.
3. find the sum of both colums
4. plug them into your formula
5. do your order of operation
6. your answer should give you your SS (sum of squared deviations)
7. you need the SS to find the variance which the forumla is
and of course to find the Stan. dev you would take the square root of the variance. try this first and we can compare...