Which formula for standard deviation are you using?
If you know the population mean then you should divide by n (3 in this
case), but if you don't know the population mean and use the mean
calculated from the sample then it is more usual to use n-1 as the
denominator (this makes the variance an unbiased estimator of the
population variance). That is what the R sd function does since it is
much more common to use it on a sample rather than an entire
population.
On Sun, Jun 8, 2014 at 1:17 AM, arun <smartpink111 at yahoo.com>
wrote:> Hi,
> Please check this link:
>
http://stats.stackexchange.com/questions/25956/what-formula-is-used-for-standard-deviation-in-r
>
> A.K.
>
>
> It is my understanding that the R function SD finds the standard deviation
of a random variable or a list. Please consider the following list: { 1, 2, 3 }.
I claim that the standard deviation of this list is not 1. However, the
following R statement returns 1:
> sd ( seq(1:3) )
> What am I missing?
>
> I thank the group in advance for their responses.
>
> Bob
>
>
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--
Gregory (Greg) L. Snow Ph.D.
538280 at gmail.com