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September 11, 2012

Are you Tracking MRR? - "Mean Reciprocal Rank" Trend Monitoring

MRR is a simple numerical technique to monitor the overall relevancy performance of search engines over time. It is based on click-throughs in the search results, where a click on the top document is scored as 100%, a click on the second document is 50%, 3rd document is 33%, etc. These numbers are collected and averaged over units of time.

The absolute value of MRR is not necessarily the important statistic because each site has different content, different classes of users, and different search technology. However, the trend of MRR over time can allow a site to spot changes quickly. It can also be used to score "A/B" testing.

There are certainly more elaborate algorithms that can be used, and MRR doesn’t account for whether a user liked the document once they opened it. But having even possibly imperfect performance data that can be trended over time is better than having nothing.

Reference: http://en.wikipedia.org/wiki/Mean_reciprocal_rank

Walter Underwood (of Ultraseek, Netflix, MarkLogic fame) gave a presentation (in PPT/PowerPoint) of this topic a couple years ago about NetFlix's use of MRR.


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