title: Estimating physical activity from incomplete accelerometer data in field studies.
abstract: BACKGROUND
  The purpose of this study was to develop a data-driven approach for analyzing incomplete accelerometer data from field-base studies.
  
  
  METHODS
  Multiple days of accelerometer data from the Stanford Girls health Enrichment Multi-site Studies (N = 294 African American girls) were summed across each minute of each day to produce a composite weekday and weekend day. Composite method estimates of physical activity were compared with those derived from methods typically described in the literature (comparison methods).
  
  
  RESULTS
  The composite method retained 99.7% and 100% of participants in weekday and weekend-day analysis, respectively, versus 84.7% to 94.2% and 28.6% to 99.0% for the comparison methods. Average wearing times for the composite method for weekday and weekend day were 99.6% and 98.6%, respectively, 91.7% to 93.9% and 82.3% to 95.4% for the comparison methods. Composite-method physical activity estimates were similar to comparison-methods estimates.
  
  
  CONCLUSIONS
  The composite method used more available accelerometer data than standard approaches, reducing the need to exclude periods within a day, entire days, and participants from analysis.
authors: Dept of Kinesiology, University of Massachusetts, Amherts, MA 01003-0258, USA.
authors: Sofiya
authors: S
authors: Alhassan
authors: John R
authors: JR
authors: Sirard
authors: Tirzah R
authors: TR
authors: Spencer
authors: Ann
authors: A
authors: Varady
authors: Thomas N
authors: TN
authors: Robinson
mesh_terms: D015992:Body Mass Index; D002648:Child; D003625:Data Collection / Q000379:methods*; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D018670:Monitoring, Ambulatory / Q000379:methods; D015203:Reproducibility of Results