The Measurement of Classification Agreement: An Adjustment to the Rand Statistic for Chance Agreement

Investigators examining empirically derived classifications are often concerned with the replicability of an obtained classification. However, most available statistics which allow replication comparison suffer from various limitations. This paper proposes an adjustment to one of these statistics, the Rand statistic, which will allow comparison across different levels for number of clusters found within a classification. This adjustment permits the user to compare several different classifications with respect to classification agreement, while correcting for the contribution of chance to any observed agreement.