Title
Position Bias Estimation for Unbiased Learning to Rank in Personal Search.
Abstract
A well-known challenge in learning from click data is its inherent bias and most notably position bias. Traditional click models aim to extract the ‹query, document› relevance and the estimated bias is usually discarded after relevance is extracted. In contrast, the most recent work on unbiased learning-to-rank can effectively leverage the bias and thus focuses on estimating bias rather than relevance [20, 31]. Existing approaches use search result randomization over a small percentage of production traffic to estimate the position bias. This is not desired because result randomization can negatively impact users' search experience. In this paper, we compare different schemes for result randomization (i.e., RandTopN and RandPair) and show their negative effect in personal search. Then we study how to infer such bias from regular click data without relying on randomization. We propose a regression-based Expectation-Maximization (EM) algorithm that is based on a position bias click model and that can handle highly sparse clicks in personal search. We evaluate our EM algorithm and the extracted bias in the learning-to-rank setting. Our results show that it is promising to extract position bias from regular clicks without result randomization. The extracted bias can improve the learning-to-rank algorithms significantly. In addition, we compare the pointwise and pairwise learning-to-rank models. Our results show that pairwise models are more effective in leveraging the estimated bias.
Year
DOI
Venue
2018
10.1145/3159652.3159732
WSDM 2018: The Eleventh ACM International Conference on Web Search and Data Mining Marina Del Rey CA USA February, 2018
Keywords
Field
DocType
Position bias estimation, inverse propensity weighting, expectation-maximization
Data mining,Pairwise comparison,Learning to rank,Regression,Computer science,Expectation–maximization algorithm,Click model,Pointwise
Conference
ISBN
Citations 
PageRank 
978-1-4503-5581-0
33
0.90
References 
Authors
27
5
Name
Order
Citations
PageRank
Xuanhui Wang1139468.85
Nadav Golbandi243618.68
Michael Bendersky398648.69
Donald Metzler43138141.39
Marc A. Najork52538278.16