# Thread: Variance of the sample mean formula.

1. ## Variance of the sample mean formula.

Suppose you are sampling a population with mean of 1,065 and standard deviation of 500. The sample size is 100. What are the expected value and the variance of the sample mean?

I know how to get expected value, I do not know how to get the variance of the sample mean though, the formula would be so helpful.

2. IF the sample is i.i.d. (indep and identically distributed), then

$E(\bar X)=E(X_1)=\mu$ ..... I mean MOooooo

$V(\bar X)={V(X_1)\over n}={\sigma^2\over n}$