The continued search for nonarbitrary metrics in psychology.

Abstract

H. Blanton and J. Jaccard examined the arbitrariness of metrics in the context of 2 current issues: (a) the measurement of racial prejudice and (b) the establishment of clinically significant change. According to Blanton and Jaccard, although research findings are not undermined by arbitrary metrics, individual scores and score changes may not be meaningfully interpreted. The author believes that their points are mostly valid and that their examples were appropriate. However, Blanton and Jaccard's article does not lead directly to solutions, nor did it adequately describe the scope of the metric problem. This article has 2 major goals. First, some prerequisites for nonarbitrary metrics are presented and related to Blanton and Jaccard's issues. Second, the impact of arbitrary metrics on psychological research findings are described. In contrast to Blanton and Jaccard (2006), research findings suggest that metrics have direct impact on statistics for group comparisons and trend analysis.