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| 153 |
if [[theta]]corresponds to a value of [[lambda]]at which an increase in recall is produced
...G s R [[theta]]s,P [[theta]]s the set of observed points for a request
...Ps R sup P:R >R s
...where R is a standard recall value
...The set of observed points is such that the interpolated function is monotonically decreasing
...In Figure 7
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| 180 |
effectiveness can be calculated to infinite precision we may be insisting on a difference when in fact it only occurs in the tenth decimal place
...Finally,although I have just explained the use of the sign test in terms of single number measures,it is also used to detect a significant difference between precision recall graphs
...Bibliographic remarks Quite a number of references to the work on evaluation have already been given in the main body of the chapter
...Buried in the report by Keen Digger [32]Chapter 16 is an excellent discussion of the desirable properties of any measure of effectiveness
...A parameter which I have mentioned in passing but which deserves closer study in generality
...The trade off between precision and recall has for a long time been the subject of debate
...Guazzo [39]describe an approach to the measurement of retrieval effectiveness based on information theory
...The notion of relevance has at all times attracted much discussion
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| 152 |
for which average precision values are calculated by averaging over all queries the individual precision values corresponding to the standard recall values
...Interpolation Many interpolation techniques have been suggested in the literature
...IMG SRC Fig
...Figure 7
...It is an experimental fact that average precision recall graphs are monotonically decreasing
...Let R [[lambda]],P [[lambda]]be the set of precision recall values obtained by varying some parameter [[lambda]]... |
| 168 |
Foundation Problems of measurement have arisen in physics,psychology,and more recently,the social sciences
...The problems of measurement in information retrieval differ from those encountered in the physical sciences in one important aspect
...The next three sections are substantially the same as those appearing in my paper:Foundations of evaluation,Journal of Documentation,30,365 373 1974
...no reason why we cannot postulate a particular ordering,or,to put it more mildly,why we can not show that a certain model for the measurement of effectiveness has acceptable properties
...1 all properties ascribed are consistent;2 they bring out into the open all the assumptions made in measuring effectiveness;3 each property has an acceptable interpretation;4 the model leads to a plausible measure of effectiveness
...It is as well to point out here that it does not lead to a uniquemeasure,but it does show that certain classes of measures can beregarded as being equivalent
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| 150 |
value can be calculated
...For a derivation of this relation from Bayes Theorem,the reader should consult the author s recent paper on retrieval effectiveness [10]...Averaging techniques The method of pooling or averaging of the individual P R curves seems to have depended largely on the retrieval strategy employed
...where As is the set of documents relevant to request s
...where B [[lambda]]s is the set of documents retrieved at or above the co ordination level [[lambda]]...Figure 7
...An alternative approach to averaging is macro evaluation which can be independent of any parameter such as co ordination level
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