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 <smartpink...@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 > > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. -- Gregory (Greg) L. Snow Ph.D. 538...@gmail.com ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
