Let Xi:j denote the ith order statistic of a random sample of size j from a continuous life distribution. We show that if Xk:n, is IFR, IFRA, NBU, or DMRL, so are Xk+1:n, Xk+1:n-1 and Xk+1:n+1. Further we show that, in the first three cases, Xk+1:n+2 also shares the corresponding property if k ≤ (n+3)/2. We also present dual results for DFR, DFRA and NWU classes.
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