title: Accuracy and consistency of weights provided by home bathroom scales.
abstract: BACKGROUND
  Self-reported body weight is often used for calculation of Body Mass Index because it is easy to collect. Little is known about sources of error introduced by using bathroom scales to measure weight at home. The objective of this study was to evaluate the accuracy and consistency of digital versus dial-type bathroom scales commonly used for self-reported weight.
  
  
  METHODS
  Participants brought functioning bathroom scales (n=18 dial-type, n=43 digital-type) to a central location. Trained researchers assessed accuracy and consistency using certified calibration weights at 10 kg, 25 kg, 50 kg, 75 kg, 100 kg, and 110 kg. Data also were collected on frequency of calibration, age and floor surface beneath the scale.
  
  
  RESULTS
  All participants reported using their scale on hard surface flooring. Before calibration, all digital scales displayed 0, but dial scales displayed a mean absolute initial weight of 0.95 (1.9 SD) kg. Digital scales accurately weighed test loads whereas dial-type scale weights differed significantly (p<0.05). Imprecision of dial scales was significantly greater than that of digital scales at all weights (p<0.05). Accuracy and precision did not vary by scale age.
  
  
  CONCLUSIONS
  Digital home bathroom scales provide sufficiently accurate and consistent weights for public health research. Reminders to zero scales before each use may further improve accuracy of self-reported weight.
authors.forename: Meredith
authors.initials: M
authors.lastname: Yorkin
authors.forename: Kim
authors.initials: K
authors.lastname: Spaccarotella
authors.affiliation: Department of Nutritional Sciences, Rutgers, The State University of New Jersey, 26 Nichol Avenue, Davison Hall, 08901, New Brunswick, NJ, USA. jmartin@njaes.rutgers.edu.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Martin-Biggers
authors.forename: Virginia
authors.initials: V
authors.lastname: Quick
authors.forename: Carol
authors.initials: C
authors.lastname: Byrd-Bredbenner
mesh_terms: D001835:Body Weight; D002138:Calibration / Q000592:standards; D004867:Equipment Design / Q000706:statistics & numerical data; D006801:Humans; D015203:Reproducibility of Results; D014894:Weights and Measures / Q000295:instrumentation*