In a one-way analysis of variance, positive-part shrinkage versions of the
R-estimators for the additive treatment constants are proposed, a long with amodified James-Stein estimation rule, when it is doubtful whether the parameters are null. The asymptotic distributional risks of the
R-estimators, the proposed estimators, and the preliminary-test and shrinkage
R-versions under an arbitrary quadratic loss are derived, and the relative risks arc studied. Under a special feasible quadratic loss, it is shown that the positive-part shrinkage
R-estimators dominate the other estimators.
R-estimators for the grand mean and for population means are discussed. The same discussions are presented for versions of the
M-estimation.
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