Classification with Reject Option: Distribution-free Error Guarantees via Conformal Prediction

Fuente: arXiv
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Main Authors: Szabadváry, Johan Hallberg, Löfström, Tuwe, Johansson, Ulf, Sönströd, Cecilia, Ahlberg, Ernst, Carlsson, Lars
Format: Preprint
Published: 2025
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author Szabadváry, Johan Hallberg
Löfström, Tuwe
Johansson, Ulf
Sönströd, Cecilia
Ahlberg, Ernst
Carlsson, Lars
author_facet Szabadváry, Johan Hallberg
Löfström, Tuwe
Johansson, Ulf
Sönströd, Cecilia
Ahlberg, Ernst
Carlsson, Lars
contents Machine learning (ML) models always make a prediction, even when they are likely to be wrong. This causes problems in practical applications, as we do not know if we should trust a prediction. ML with reject option addresses this issue by abstaining from making a prediction if it is likely to be incorrect. In this work, we formalise the approach to ML with reject option in binary classification, deriving theoretical guarantees on the resulting error rate. This is achieved through conformal prediction (CP), which produce prediction sets with distribution-free validity guarantees. In binary classification, CP can output prediction sets containing exactly one, two or no labels. By accepting only the singleton predictions, we turn CP into a binary classifier with reject option. Here, CP is formally put in the framework of predicting with reject option. We state and prove the resulting error rate, and give finite sample estimates. Numerical examples provide illustrations of derived error rate through several different conformal prediction settings, ranging from full conformal prediction to offline batch inductive conformal prediction. The former has a direct link to sharp validity guarantees, whereas the latter is more fuzzy in terms of validity guarantees but can be used in practice. Error-reject curves illustrate the trade-off between error rate and reject rate, and can serve to aid a user to set an acceptable error rate or reject rate in practice.
format Preprint
id arxiv_https___arxiv_org_abs_2506_21802
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Classification with Reject Option: Distribution-free Error Guarantees via Conformal Prediction
Szabadváry, Johan Hallberg
Löfström, Tuwe
Johansson, Ulf
Sönströd, Cecilia
Ahlberg, Ernst
Carlsson, Lars
Machine Learning
Machine learning (ML) models always make a prediction, even when they are likely to be wrong. This causes problems in practical applications, as we do not know if we should trust a prediction. ML with reject option addresses this issue by abstaining from making a prediction if it is likely to be incorrect. In this work, we formalise the approach to ML with reject option in binary classification, deriving theoretical guarantees on the resulting error rate. This is achieved through conformal prediction (CP), which produce prediction sets with distribution-free validity guarantees. In binary classification, CP can output prediction sets containing exactly one, two or no labels. By accepting only the singleton predictions, we turn CP into a binary classifier with reject option. Here, CP is formally put in the framework of predicting with reject option. We state and prove the resulting error rate, and give finite sample estimates. Numerical examples provide illustrations of derived error rate through several different conformal prediction settings, ranging from full conformal prediction to offline batch inductive conformal prediction. The former has a direct link to sharp validity guarantees, whereas the latter is more fuzzy in terms of validity guarantees but can be used in practice. Error-reject curves illustrate the trade-off between error rate and reject rate, and can serve to aid a user to set an acceptable error rate or reject rate in practice.
title Classification with Reject Option: Distribution-free Error Guarantees via Conformal Prediction
topic Machine Learning
url https://arxiv.org/abs/2506.21802