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This research examined the relationship between subjects' knowledge of an area and their similarity ratings of pairs of concepts. Knowledge was operationalized as (1) test score performance, and (2) correspondence with an expert's similarity judgments. Subjects (n=55) were exposed to a three-week module on social psychology as part of their introductory psychology course. At the end of this course segment they were administered an examination and, later, a term similarity questionnaire. Students' similarity ratings related to both exam score and similarity ratings of the expert. Furthermore, as expected, test performance was strongly related (r=+.55) to the correlation with the expert's similarity judgments. A model based on term similarity judgments was proposed as a theoretical explanation of how term dependence models influence information retrieval system performance.

Abstract This study examined the effectiveness and efficiency of employing a fully automatic algorithm for ranking the results of Boolean searches of an inverted file design document retrieval system. The study indicated that with minor modification of file designs, such as those implemented in the Syracuse Information Retrieval Experiment (SIRE), document retrieval systems could efficiently provide users with output lists on which the rank order of a document is a good indicator of its probable relevance to the user's information need. The study found that relevant documents were ranked significantly higher than nonrelevant documents in the set of documents retrieved in response to a Boolean query. By utilizing an augmented inverted file design the variable incremental cost for ranked output was only ten cents per query. There was no increased user effort.