A graphical judgmental aid which summarizes obtained and chance reliability data and helps assess the believability of experimental effects.

Interval by interval reliability has been criticized for "inflating" observer agreement when target behavior rates are very low or very high. Scored interval reliability and its converse, unscored interval reliability, however, vary as target behavior rates vary when observer disagreement rates are constant. These problems, along with the existence of "chance" values of each reliability which also vary as a function of response rate, may cause researchers and consumers difficulty in interpreting observer agreement measures. Because each of these reliabilities essentially compares observer disagreements to a different base, it is suggested that the disagreement rate itself be the first measure of agreement examined, and its magnitude relative to occurrence and to nonoccurrence agreements then be considered. This is easily done via a graphic presentation of the disagreement range as a bandwidth around reported rates of target behavior. Such a graphic presentation summarizes all the information collected during reliability assessments and permits visual determination of each of the three reliabilities. In addition, graphing the "chance" disagreement range around the bandwidth permits easy determination of whether or not true observer agreement has likely been demonstrated. Finally, the limits of the disagreement bandwidth help assess the believability of claimed experimental effects: those leaving no overlap between disagreement ranges are probably believable, others are not.