title: Validity and repeatability of a modified Baecke questionnaire on physical activity.
abstract: BACKGROUND
  In a pilot study for the European Prospective Investigation into Cancer and Nutrition (EPIC) a modification of the Baecke questionnaire on physical activity was tested for repeatability and relative validity in a population of 134 men and women aged 20-70 years.
  
  
  METHODS
  For the assessment of repeatability Pearson's correlation coefficients and percentages of agreement after classification in tertiles were computed between administrations of the questionnaire at baseline, and after 5 and 11 months. Relative validity was determined by comparing the questionnaire to a four times repeated 3-day activity diary.
  
  
  RESULTS
  Repeatability after 5 and 11 months was good, with test-retest correlation coefficients between 0.65 and 0.89 for main sections of the questionnaire. The percentages of agreement, exceeding chance (Cohen's kappa) were 57% and 56% for men (at 5 and 11 months respectively) and 41% and 46% for women. The correlations with the diaries were 0.56 in men and 0.44 in women. Agreement apart from chance between classification in tertiles for both methods was 35% for men and 10% for women.
  
  
  CONCLUSIONS
  These data show that repeatability is good and relative validity as compared to an activity diary is moderate but well within the range of values found in other studies. The questionnaire is more valid in men than in women.
authors.affiliation: Department of Epidemiology, Faculty of Medicine, University of Utrecht, The Netherlands.
authors.forename: M A
authors.initials: MA
authors.lastname: Pols
authors.forename: P H
authors.initials: PH
authors.lastname: Peeters
authors.forename: H B
authors.initials: HB
authors.lastname: Bueno-De-Mesquita
authors.forename: M C
authors.initials: MC
authors.lastname: Ocké
authors.forename: C A
authors.initials: CA
authors.lastname: Wentink
authors.forename: H C
authors.initials: HC
authors.lastname: Kemper
authors.forename: H J
authors.initials: HJ
authors.lastname: Collette
mesh_terms: D000328:Adult; D000368:Aged; D016009:Chi-Square Distribution; D015331:Cohort Studies; D015930:Diet Records; D004734:Energy Metabolism; D015444:Exercise; D005260:Female; D006801:Humans; D007899:Leisure Activities; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D011594:Psychometrics; D012016:Reference Values; D015203:Reproducibility of Results; D012737:Sex Factors; D013177:Sports; D011795:Surveys and Questionnaires