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arXiv · 2303.11706

Lower bounds for the trade-off between bias and mean absolute deviation

Alexis Derumigny·Johannes Schmidt-Hieber
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Abstract

In nonparametric statistics, rate-optimal estimators typically balance bias and stochastic error. The recent work on overparametrization raises the question whether rate-optimal estimators exist that do not obey this trade-off. In this work we consider pointwise estimation in the Gaussian white noise model with regression function $f$ in a class of $β$-Hölder smooth functions. Let 'worst-case' refer to the supremum over all functions $f$ in the Hölder class. It is shown that any estimator with worst-case bias $\lesssim n^{-β/(2β+1)}=: ψ_n$ must necessarily also have a worst-case mean absolute deviation that is lower bounded by $\gtrsim ψ_n.$ To derive the result, we establish abstract inequalities relating the change of expectation for two probability measures to the mean absolute deviation.

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Alexis Derumigny, Johannes Schmidt-Hieber. 2024-06-20. Lower bounds for the trade-off between bias and mean absolute deviation. https://doi.org/10.1016/j.spl.2024.110182

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