Percentage agreement and phi: A conversion table.

STUDIES IN APPLIED BEHAVIOR ANALYSIS HAVE USED TWO EXPRESSIONS OF RELIABILITY FOR HUMAN OBSERVATIONS: percentage agreement (including percentage occurrence and percentage nonoccurrence agreement) and correlational techniques (including the phi coefficient). The formal relationship between these two expressions is demonstrated, and a table for converting percentage agreement to phi, or vice-versa, is presented. It is suggested that both expressions be reported in order to communicate reliability unambiguously and to facilitate comparison of the reliabilities from different studies.