pp) for estimation of the $p_r$th probability of the $r$th order statistic for a sample of size $n$: the mean is $p'_r = r/(n+1)$ (Weibull plotting position) and the median is $p^\star_r = IIB(0.5, r, n+1-r)$, where $f$ represents the nonexceedance probability of the plotting position. $IIB$ is the qbeta(f, a, b). If $f=0.5$, then the median is returned but conveniently implemented in pp.median. See Gilchrist (2011, chapter 12, p. 510 in Karian and Dudewicz, 2011).pp.f(f, x)vector is returned.pp pp.median