Deviation and excel - different than calculated?

Question

This is driving me nuts. Any math wizz answer this for me please:

Why am I getting different deviation values when I work it out on paper than when I use excel. Heres the problem:

Average: 50.08
5 tests: 50.11, 50.08, 50.10, 50.07, 50.05

By hand I get: .0239791576
With excel I get .023874673

Am I working this out right? What did you get when you did both? Thanks in advance.

Answer 1

I tried several calculations and found where you went wrong.

You list the mean as 50.08. However, this value is not correct. The true mean of the set is 50.082. When you use 50.082, you will get the correct value (the one Excel got).

Don't ever round results until the very end, otherwise you introduce systematic errors into your calculation.

Answer 2

commonplace deviation bars would desire to be plus or minus a million commonplace deviation from the mean. so if mean =10 and primary deviation= 2 then you certainly would have a bar going from 12 to eight with a factor at 10 to mark the mean. i think of there are frequently refered to as errors bars. If we are able to assume that the distribution is regularly occurring then around sixty 8% of the outcomes would desire to lie interior the errors/commonplace deviation bars.