Stochastic Comparisons Between Sample Spacings of Order Statistics from Independent Exponential Random Variables

Suppose there are two groups of independent exponential random variables، where the first group has different hazard rates and the second group has common hazard rate. In this paper، the various stochastic orderings between their sample spacings have studied and introduced some necessary and sufficient conditions to equivalence of these stochastic ordering. Also، for the special case of sample size two، it is shown that the hazard rate function of the second sample spacing is Shcur-concave in the inverse vector of parameters.