Okay simple question about the populationstandard deviation

I have the following: the expected value and the variance of a PDF.

I am running 3 simulations with n=10,n=20, and n=30.

I need the population standard deviation of the mean of a sample size n from your distribution

I thought it would be just the square root of the (variance/n), is that not correct? (so thus 3 different sd's.

Or is it simply the square root of the variance?

Further on I am asked to find the table of the proportion of means within one and two stadard deviations of E(X), and I use the following code:

mean(abs(xbar10-mu)<sqrt(var/n))

which would mean the sqrt(var/n) is the standard deviation, correct?