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Loss minimization and parameter estimation with heavy tails. (English) Zbl 1360.62380
Summary: This work studies applications and generalizations of a simple estimation technique that provides exponential concentration under heavy-tailed distributions, assuming only bounded low-order moments. We show that the technique can be used for approximate minimization of smooth and strongly convex losses, and specifically for least squares linear regression. For instance, our $$d$$-dimensional estimator requires just $$\tilde{O}(d\log(1/\delta))$$ random samples to obtain a constant factor approximation to the optimal least squares loss with probability $$1-\delta$$, without requiring the covariates or noise to be bounded or subgaussian. We provide further applications to sparse linear regression and low-rank covariance matrix estimation with similar allowances on the noise and covariate distributions. The core technique is a generalization of the median-of-means estimator to arbitrary metric spaces.

##### MSC:
 62J05 Linear regression; mixed models 62F10 Point estimation 62J07 Ridge regression; shrinkage estimators (Lasso)
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