Caroline Giacobino | Searcharxiv

arXiv2018

Thresholding tests

We derive a new class of statistical tests for generalized linear models based on thresholding point estimators. These tests can be employed whether the model includes more parameters than observations or not. For linear models, our tests rely on pivotal statistics derived from model selection techniques. Affine lasso, a new extension of lasso, allows to unveil new tests and to develop in the same framework parametric and nonparametric tests. Our tests for generalized linear models are based on new asymptotically pivotal statistics. A composite thresholding test attempts to achieve uniformly most power under both sparse and dense alternatives with success. In a simulation, we compare the level and power of these tests under sparse and dense alternative hypotheses. The thresholding tests have a better control of the nominal level and higher power than existing tests.

stat.ME↗

arXiv2017

Quantile universal threshold for model selection

Efficient recovery of a low-dimensional structure from high-dimensional data has been pursued in various settings including wavelet denoising, generalized linear models and low-rank matrix estimation. By thresholding some parameters to zero, estimators such as lasso, elastic net and subset selection allow to perform not only parameter estimation but also variable selection, leading to sparsity. Yet one crucial step challenges all these estimators: the choice of the threshold parameter~$λ$. If too large, important features are missing; if too small, incorrect features are included. Within a unified framework, we propose a new selection of $λ$ at the detection edge under the null model. To that aim, we introduce the concept of a zero-thresholding function and a null-thresholding statistic, that we explicitly derive for a large class of estimators. The new approach has the great advantage of transforming the selection of $λ$ from an unknown scale to a probabilistic scale with the simple selection of a probability level. Numerical results show the effectiveness of our approach in terms of model selection and prediction.

stat.ME↗