Recall on the web recall seldom marers what marers

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Unformatted text preview: judgments of whether documents are relevant to queries Then we can use Precision/Recall/F measure as before §༊  Evalua*on of ranked results: §༊  The system can return any number of results §༊  By taking various numbers of the top returned documents (levels of recall), the evaluator can produce a precision- recall curve 71 Introduc)on to Informa)on Retrieval Recall/Precision R P §༊  §༊  §༊  §༊  §༊  §༊  §༊  §༊  §༊  §༊  1 2 3 4 5 6 7 8 9 10 R N N R R N R N N N Assume 10 rel docs in collection Introduc)on to Informa)on Retrieval Sec. 8.4 A precision- recall curve 1.0 Precision 0.8 0.6 0.4 0.2 0.0 0.0 0.2 0.4 0.6 0.8 1.0 Recall 73 Introduc)on to Informa)on Retrieval Sec. 8.4 Averaging over queries §༊  A precision- recall graph for one query isn’t a very sensible thing to look at §༊  You need to average performance over a whole bunch of queries. §༊  But there’s a technical issue: §༊  Precision- recall calcula*ons place some points on the graph §༊  How do you determine a value (interpolate) between the points? 74 Introduc)on to Informa)on Retrieval Sec. 8.4 Inte...
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