Difference between standard deviation equations...

Question

adamaero · Answer

http://psyc261green.files.wordpress.com/2008/02/sdddddddddd.gif http://s2.hubimg.com/u/6951521_f260.jpg When should I use one opposed to the other?

adamaero · Answer

@jim_thompson5910

jim_thompson5910 · Answer

the only difference is between the "n" and "n-1" in the denominator

jim_thompson5910 · Answer

you use the "n-1" version when finding the sample standard deviation

the other formula is for finding the population standard deviation

adamaero · Answer

I know; that's what makes it so confusing

jim_thompson5910 · Answer

usually you do NOT know much about the population since it is way too big

so this is why samples are used to represent it and make a good educated guess. This is assuming you sampled correctly

jim_thompson5910 · Answer

so for the most part, you'll use the sample standard deviation because you won't know your whole population

if you have a problem that only cares about a group of 10 people, and only those people, then you'll likely use the population version

adamaero · Answer

So just n
for population?

adamaero · Answer

I'll assume so.

jim_thompson5910 · Answer

n for population
n-1 for sample