What would you call this type of average?
$\left(\frac{1}{n} \sum_{i=1}^n \sqrt x_i \right) ^ 2$
What would you call this type of average?
$\left(\frac{1}{n} \sum_{i=1}^n \sqrt x_i \right) ^ 2$
This is moderately special, but I don't think it is special enough to have its own name.
I would call it "1/2-power mean", with a possible explanation that the "$r$-power mean" of $(a_i)_{i=1}^n$ is $ (\frac1{n} \sum_{i=1}^n a_i^{r})^{1/r} $".
Because it isn't used nearly as often as the arithmetic mean, geometric mean, or RMS, this mean doesn't have a common name other than just "the generalized mean with $p=1/2$".