Inadmissibility Results for the Selected Hazard Rates
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Let us consider k (≥ 2) independent populations Π_1, …,Π_k, where Π_i follows exponential distribution with hazard rate σ_i, (i = 1,…,k). Suppose Y_i1,…, Y_in be a random sample of size n drawn from the ith population Π_i, where i = 1,…,k. For i = 1,…,k, consider Y_i=∑_j=1^nY_ij. The natural selection rule is to select a population associated with the largest sample mean. That is, Π_i, (i = 1,…,k) is selected if Y_i=max(Y_1,…,Y_k). Based on this selection rule, a population is chosen. Then, we consider the estimation of the hazard rate of the selected population with respect to the entropy loss function. Some natural estimators are proposed. The minimaxity of a natural estimator is established. Improved estimators improving upon the natural estimators are derived. Finally, numerical study is carried out in order to compare the proposed estimators in terms of the risk values.
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