# If $x$ is a $p$-value, what do we call $x\cdot (1-x)$?

What do you call this function?

$$f(x) = x(1 - x)$$

Does it have a name? It’s cropped up in at least two statistical formulas I've been asked to program so far. (In both cases, $x$ was something called a $p$-value (for what it's worth).)

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## 1 Answer

If Z can take values 1 or 0 with probability x and 1-x, respectively, we usually call x*(1-x) the variance of Z.

This is a special case of the more general variance formula, and works because Z is what we call an indicator variable.

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