A Partial Solution to the Base Rate Problem of the k Statistic

To the Editor.—  Recently there has been a dispute among experts concerning the measurement of diagnostic agreement^1-3 and the use of the k statistic.⁴ We share the view of Uebersax⁵ that the real solution to this problem will require new paradigms for assessing interjudge agreement, and in particular that the more expensive multiple-judge designs or criteriondiagnosis designs are desirable. However, we do not accept that developing correction formulas to equate k values obtained from samples with different base rates is pointless.^2,5 Under the conventional models for psychiatric diagnosis that underlie the calculation of k, it is possible to adjust k so as to incorporate base rate differences. This adjustment does not address the more complex issues raised,^1,2,5 but may go some way toward reconciling divergent views^2,3 about k.Following Spitznagel and Helzer,¹ we define the sensitivity of a judge as the probability of