Cognitive Interviewing: A Qualitative Tool for Improving Questionnaires in Sport Science

This study sought to determine whether body fat percentage estimates using an inexpensive bioelectrical impedance analysis (BIA) device (Tanita TBF-521, Tanita Corp, of America, Arlington Heights, IL) could be freely substituted for those obtained utilizing skinfolds (method equivalence). Data were analyzed from measurements on 38 children age 6 to 12 years. Random effect intraclass correlation (r = .930; 95% confidence interval [CI] = .87 to .96), fixed effect intraclass correlation (r = .932; 95% CI = .87 to .96), and least-products regression supported the equivalence of the 2 methods. The technical error between the 2 methods (3.7; coefficient of variation = 12.2%) was small and also supported the equivalence of the two methods. The ability of the BIA device to categorize into normal and obese categories when compared to the skinfold technique was also impressive (κ = .95; 95% CI = .73 to .99). However, the results of the limits of agreement analysis showed that the approximate 95% CI for the differences between methods was wide (-9.1 to 11.4).