Against Standard Deviation as a Quality Control Maxim in Anthropometry

Anthropometry is the study of the measurements and proportions of the human body. In the field, many practitioners have adopted a questionable quality control maxim. The maxim is, essentially, to dismiss any survey of anthropometric measurements whose standard deviation exceeds that of a benchmark survey, sample, or distribution by some amount (e.g., 30 percent). To date there is no published study which properly substantiates the maxim. Despite the lack of sound statistical justification and lack of scientific evidence, the standard deviation as quality control indicator persists. Practitioners who endorse the maxim transpose the conditional and muddle samples with populations and references with standards. The practice is endemic and may have real consequences in terms of financial resources and global morbidity and mortality. This paper details the genesis and propagation of the maxim in the literature, exposes its theoretical and logical weaknesses, illustrates its demerits, and offers an alternative attitude toward the problem of quality control.