Page 162 Concepts and similar pages

Concepts

Similarity Concept
Measures of effectiveness
Measurement of effectiveness
Effectiveness
Relevance
E measure
Indexing
Document clustering
Document representative
Statistical significance
Typical document

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163 normalising the ESL by a factor proportional to the expected number of non relevant documents collected for each relevant one ...which has been called the expected search length reduction factor by Cooper ...where 1 R is the total number of documents in the collection relevant to q;2 I is the total number of documents in the collection non relevant to q;3 S is the total desired number of documents relevant to q ...The explicit form for ESL was given before ...which is known as the mean expected search length reduction factor ...Within the framework as stated at the head of this section this final measure meets the bill admirably ...For a further defence of its subjective nature see Cooper [1]...
160 system so that if we were to adopt [[Delta]]as a measure of effectiveness we could be throwing away vital information needed to make an extrapolation to the performance of other systems ...The Cooper model expected search length In 1968,Cooper [20]stated:The primary function of a retrieval system is conceived to be that of saving its users to as great an extent as is possible,the labour of perusing and discarding irrelevant documents,in their search for relevant ones ...a only one relevant document is wanted;b some arbitrary number n is wanted;c all relevant documents are wanted;4 a given proportion of the relevant documents is wanted,etc ...Thus,the index is a measure of performance for a query of given type ...The output of a search strategy is assumed to be a weak ordering of documents ...