How do you find standard deviation?

I have added this thread to our reference material thread.  :)

The formula for standard deviation is:

where x represents each of the data elements, x-bar represents the average of the x-values, and n represents the number of x-values.

To do this by hand:

1) find the average of all the x-values

2) for each x-value, find the difference between the x-value and the average value, and then square that answer

3) sum all the values from step 2

4) divide the answer of step 3 by n-1, the number of values minus 1

5) find the square root of step 4.

I think that is standard deviation of a sample

For standard deviation of a population I think that you use n instead of n-1