document: Evaluating similarity measures : a large-scale study in the orkut social network Online information services have grown too large for users to navigate without the help of automated tools such as collaborative filtering , which makes recommendations to users based on their collective past behavior . While many similarity measures have been proposed and individually evaluated , they have not been evaluated relative to each other in a large real-world environment . We present an extensive empirical comparison of six distinct measures of similarity for recommending online communities to members of the Orkut social network . We determine the usefulness of the different recommendations by actually measuring users ' propensity to visit and join recommended communities . We also examine how the ordering of recommendations influenced user selection , as well as interesting social issues that arise in recommending communities within a real social network .
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