Robustness of Estimators on Stationary Observations

Abstract

Hampel's general qualitative definition of robustness of sequences of estimators on memoryless observation processes is generalized to stationary ergodic processes by substituting the generalized Ornstein (or $\bar{\phi}$) distance for the marginal Prohorov distance as the measure of "closeness" of observations. More general sequences of estimators are also allowed. The approach yields results analogous to those of Hampel for the more general case considered, often provides strict generalizations of Hampel's results, and in some cases yields simpler proofs.