The  Weizmann  Institute  of  Science
                  Faculty of Mathematics and Computer Science
 
                             Special Guest Lecture
 
                                   Ofer Dekel
                               Microsoft Research
 
                                 will speak on
 
                        Learning from Multiple Teachers
 
                     Lecture Hall, Room 1, Ziskind Building
                          on Sunday, February 14, 2010
                                    at 11:00
 
                        JOINT VISION AND FOUNDATIONS OF
                            COMPUTER SCIENCE SEMINAR
                          Please note unusual location
 
Abstract:
Supervised machine learning algorithms are typically designed under the
assumption that the labels in the training set are provided by a single
"teacher". However, in practice, labels are often collected from multiple
teachers, with different levels of expertise, competence, and motivation. In
this talk, I will present a new family of machine learning algorithms that
benefit from the presence of multiple teachers. These algorithms explicitly use
the association between labels and teachers to clean the training data and
ultimately learn more accurate models.
 
First, I will present the problem of learning from a crowd, where labeled data
is collected from the general public via a crowd-sourcing website (such as
galaxyzoo.org or mturk.com). In this setting, the average label quality is
poor, so algorithms that ignore the association between labels and teachers are
likely to produce inferior results. I will focus on the concrete problem of
identifying low-quality teachers and removing their labels from the training
data. Next, I will go on to discuss the problem of active-learning from
multiple teachers, where the learning algorithm has to decide which examples
should be labeled and which subset of teachers should label them. I will
present a new online learning algorithm for this problem, which does almost as
well as each teacher in their area of expertise. For each algorithm, I will
give a sketch of a formal analysis and present experimental results on real
datasets.
 
Parts of this work were done in collaboration with Claudio Gentile, Ohad
Shamir, and Karthik Sridharan.
 
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Technion Math Net-2 (TECHMATH2)
Editor: Gershon Wolansky <techm@math.technion.ac.il>
Announcement from: Diana Mandelik <diana.mandelik@weizmann.ac.il>