*I have found this forum through a google search and this is my first post. I usually read and ocassionally post on an astronomy forum (http://www.bautforum.com/). I have also asked this question on their Q&A section.*

I thought that maybe there might be more specialized knowledge on this forum regarding this particular subject.

Thank you in advance for taking time to ponder my questions.

I thought that maybe there might be more specialized knowledge on this forum regarding this particular subject.

Thank you in advance for taking time to ponder my questions.

I have read that the way Excel calculates standard deviation

=STDEV(A1:A9)

stdev = sqrt( (n * SUMof (samples^2) - SUMof(samples)^2) / (n* (n-1) )

The "proper" way according to some sources is:

stdev = sqrt( 1/n SUMof(( sample - mean)^2) )

=STDEV

**P**(A1:A9)Should I be concerned?

I've got a feeling that both formulas might have their merits but should be used under different circumstances. If this is right, when should I use which formula?

I did some reading but haven't really reached a conclusion for myself yet. Here are some of the links I've looked at:

http://www.maryparker.org/excel/stdev.htm

http://www.cs.uiowa.edu/~jcryer/JSMTalk2001.pdf

http://en.wikipedia.org/wiki/Standard_deviation (plus its talkpage)

Thanks for your time!