Finding information on the World Wide Web: the retrieval effectiveness of search engines

Search engines are essential for finding information on the World Wide Web. We conducted a study to see how effective eight search engines are. Expert searchers sought information on the Web for users who had legitimate needs for information, and these users assessed the relevance of the information retrieved. We calculated traditional information retrieval measures of recall and precision at varying numbers of retrieved documents and used these as the bases for statistical comparisons of retrieval effectiveness among the eight search engines. We also calculated the likelihood that a document retrieved by one search engine was retrieved by other search engines as well. (C) 1999 Elsevier Science Ltd. All rights reserved.