Reliability, dependability, and precision of anthropometric measurements. BioMed Research International 5 The second national health and nutrition examination survey 1976–1980

The components of reliability for eight anthropometric measures were studied in 95 male and 134 female subjects from the Second National Health and Nutrition Examination Survey (NHANES II). The contributions to unreliability variance (S?) that occur as a result of measuring errors (S£, imprecision variance) and of intrasubject fluctuations in a measurement due to physiologic factors (Si, unde-pendability) were estimated (S * = S2P + Si). Unreliability was then related to the between-subject variance (s*) to estimate the reliability ( 0 = 1- (Sf/s2)) of the measurement Four of the anthropometric measurements (weight, height, sitting height, and arm circumference) had reliabilities in excess of R = 0.97. In the first three of these, measurement imprecision made up two thirds or less of unreli-ability, and undependability (SI) was stable by two weeks. Lesser but still acceptable reliabilities were obtained for triceps and subscapular skinfolds, bitrochanteric breadth, and elbow breadth (R = 0.81-0.95). For these variables imprecision (SJ) was the major source of error. Furthermore, the unreliability (Sf) between observers was twice as high or more than the unreliability withi