How do I obtain a pooled mean standard error?
Suppose we have each of K people (or groups) which we wish to pool each with variances, V_$k$ and mean m$_k$ based on a sample of size n_$k}$.
$$ Pooled Variance V = \frac{\Sum_{k}(n_k}-1)V_{k}}{\Sum_{k}(n_{k}-1)} $$
$$ Pooled Mean Standard Error = \Sqrt{V / \sum_{k}n_{k}}