Quote by mathman
X_{k} is a sample from a population. n is the number of samples. All samples are from the same population, so the variance will be the same for each sample.

Here is an example from my book where they use n as number of elements in a sample to calculate standard deviation:
http://bildr.no/view/1124676
I just cant see how that is possible friom the derivation given in the link in my first post