By employing a concomitant variable, researchers can reduce the error, increase the precision, and maximize the power of an experimental design. Blocking and analysis of covariance (ANCOVA) are most often used to harness the power of a concomitant variable. Whether to block or covary and how many blocks to be used if a block design is chosen…

Discussion of online bibliographic database searches focuses on a software system, SORT-AID/SABRE, that ranks retrieved citations in terms of relevance. Results of a comprehensive user evaluation of the relevance ranking procedure to determine its effectiveness are presented, and implications for future work are suggested. (10 references) (LRW)