title: An extension of a familiar index of observer agreement.
abstract: A popular index of observer agreement is a/(a + d) in which a and d represent the number of agreements and disagreements. This article provides a rationale for the extension of the index to the multiple-observer case, a comparison with another frequently used index, a description of situations for which the index is appropriate, and an analysis of factors related to interpreting the magnitude of the index.
mesh_terms: D001288:Attention; D004192:Discrimination, Psychological; D006801:Humans; D011338:Probability Theory; D013070:Speech Therapy / Q000379:methods*; D013342:Stuttering / Q000175:diagnosis*