I'm reading a peer-reviewed article from a highly respected member of my field. In it the author defines equations for the mean and variance of the mean.
I'm trying to understand why the denominator for variance has both n and n-1 in it. I thought the basic equation for variance from a simple random sample was simply
$\frac{1}{n}$ $\sum^{n}_{i=1} (x_{i} - \bar x ) ^ 2 $
and it seems like this author has added an additional component to the denominator- which changes the value of the variance substantially. Can someone enlighten me?