## Qualitative robustness for stochastic processes.(English)Zbl 0644.62037

Defining appropriate metrics between samples, the authors generalize Hampel’s concept of qualitative robustness of a sequence of estimators ($$\pi$$-robustness) to the case of stochastic processes. Also a new approach to qualitative robustness is presented, based on the intuitive concept of resistance, where instead of considering the insensitivity of estimates with respect to small changes in distribution of a process, the insensitivity corresponds to a given sample point $$x\in X^{\infty}$$. Resulting concepts of (asymptotic) strong and weak resistance are then related to $$\pi$$-robustness.
It is shown, in particular, that when a finite-dimensional parameter is estimated, then $$\pi$$-robustness is equivalent to the weak resistance. The authors also prove that a class of estimates which includes generalized M-estimates (GM-estimates) for linear models and autoregressive processes is strongly resistant.
Reviewer: T.Bednarski

### MSC:

 62F35 Robustness and adaptive procedures (parametric inference) 62M10 Time series, auto-correlation, regression, etc. in statistics (GARCH)
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