🚀 go-pugleaf

In article <1992Aug14.172833.11844@cbfsb.cb.att.com> rizzo@cbnewsf.cb.att.com (anthony.r.rizzo) writes:
>Can someone explain why calculating the Standard Deviation (SD),
>for small samples, with (n-1) in the denominator is better than
>doing so with (n) in the denominator?  I'm sure that there's
>a perfectly good reason for doing so.  But we, lowly engineers
>aren't usually told the reason.  Thanks now, for your response later.;-)
>
>Tony Rizzo (att.com!homxc!rizzo)
>

Well the (n-1) term is used when you have a "biased" condition.
I don't know the full theoretical reasons, but if you use "n"
instead of (n-1) your standard deviation is _smaller_. so if you
are less than sure that your sample is truely representative of
your population you use "n-1" which provides for a slightly
larger standard deviation.  Of course when you are dealing with
very small samples (n < 30 maybe) this could make a heck of a
difference in the resulting std. dev. value.

chris