Note that this function computes the quartiles using the
`quantile`

function rather than following
Tukey's recommendations,
i.e., `IQR(x) = quantile(x, 3/4) - quantile(x, 1/4)`

.

For normally \(N(m,1)\) distributed \(X\), the expected value of
`IQR(X)`

is `2*qnorm(3/4) = 1.3490`

, i.e., for a normal-consistent
estimate of the standard deviation, use `IQR(x) / 1.349`

.