Subset selection based on order statistics from logistic populations

Consider k equal size treatment groups and let the outcome of interest be a survival time. Suppose that a known monotone transformation of the surviva l times is logistically distributed and that the treatment only affects the location parameter. We obtain exact results for the problem of selecting a subset of treatments, based on the i-th ordered survival times, which cont ains with specified probability P* the optimal treatment. Since the distribution of the median of a small logistic i.i.d. sample is s hown to approximate very well the normal distribution our exact results for the median can also be used for subset selection based on estimates of loc ation parameters which are normally or approximately normally distributed.