Technion, IEM faculty - Statistics Seminar Speaker: Yair Wiener Title: Selective Classification and Active Learning: Two Sides Of the Same Coin ? Date: 22/05/2011 Time: 14:30 Place: Bloomfield-527 Abstract: <http://ie.technion.ac.il/seminar_files/1303513772_wiener.pdf> Or read here: An ongoing challenge in machine learning is the development of formal performance guarantees for learning algorithms. Given a labeled sample, our goal is to generate both a classifier and an upper bound on its expected error. In this talk we explore a method for improving the error bound by compromising its coverage (a learning model termed selective classification or classification with a reject option). For the realizable case we will show that perfect classification (zero test error) can be guaranteed even for finite sample sizes. Using known results from statistical geometry we will derive upper bound on the rejection rate and show that for many real life problems a meaningful coverage can be guaranteed. We will also show a strong relation between two known learning models: stream-based active learning and perfect selective classification (an extreme case of ‘classification with a reject option’). ). For these models, restricted to the realizable case, we will show a reduction of active learning to selective classification that preserves fast rates. Applying this reduction to recent results for selective classification, we will derive exponential label complexity speedup for actively learning general (non-homogeneous) linear classifiers when the data distribution is an arbitrary high dimensional mixture of Gaussians. We will conclude by showing some recent results on the performance guarantees of agnostic selective classification. Inspired by the theory we will show a simple rejection rule that outperform the well known ambiguity reject method based on distance from SVM decision boundary. Joint work with Ran El-Yaniv --------------------------------------------------------- Technion Math. Net (TECHMATH) Editor: Michael Cwikel <techm@math.technion.ac.il> Announcement from: <ynardi@ie.technion.ac.il>