Which one you should use depends on which one you need for your next set of
calculations. You may need both depending.
Both are valid statistics, but have different uses
The issue is not an EXCEL issue. You need to go to a statistician and
describe your needs and he will be able to determine which one you need

"sgreene" wrote:

We have 520 inputs...20 categories x 26 participants
For the Standard Deviation do we use the average of the 20 categories or the
520 inputs? We used stdevp on the 520 and got 1.1 When we used the stdevp
on the averages of the 20 categories we got .3
Can you help we are not sure which one is correct?