Defined as $$z = (0.5 - \bar{p}) \sqrt{12k}$$
which is a standard normal and due to edgington72b;textualmetap
becker94metaprosenthal78metap
The values of \(p\) should be such that \(0\le{}p\le{}1\).
A warning is issued if this means that studies are omitted
and an error results if,
possibly after deletion of illegal values, fewer than four studies remain.
The plot method for class ‘metap’ calls schweder on the valid
\(p\)-values