Discounted cumulative gain and user decision models

  • Authors:
  • Georges Dupret

  • Affiliations:
  • Yahoo!

  • Venue:
  • SPIRE'11 Proceedings of the 18th international conference on String processing and information retrieval
  • Year:
  • 2011

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Abstract

We propose to explain Discounted Cumulative Gain (DCG) as the consequences of a set of hypothesis, in a generative probabilistic model, on how users browse the result page ranking list of a search engine. This exercise of reconstructing a user model from a metric allows us to show that it is possible to estimate from data the numerical values of the discounting factors. It also allows us to compare different candidate user models in terms of their ability to describe the observed data, and hence to select the best one. It is generally not possible to relate the performance of a ranking function in terms of DCG with the clicks observed after the function is deployed on a production environment. We show in this paper that a user model make this possible. Finally, we show that DCG can be interpreted as a measure of the utility a user gains per unit of effort she is ready to allocate. This contrasts nicely with a recent interpretation given to average precision (AP), another popular Information Retrieval metric, as a measure of effort needed to achieve a unit of utility [7].