The D-L test of agreement: a stronger measure of interrater reliability

This article examines the theoretical underpinnings and the procedures of the Derdiarian-Lewis (D-L) test of proportion of complete agreement to determine reliability among raters. The D-L test yielded data produced by three raters who rated an average of 253 units of verbal content for each of six patients. The test is supported as a stronger measure of interrater reliability than the conventionally used percent agreement method.