title: The reliability and validity of the physical activity questions in the WHO health behaviour in schoolchildren (HBSC) survey: a population study.
abstract: OBJECTIVE
  To assess the test-retest reliability and validity of the physical activity questions in the World Health Organisation health behaviour in schoolchildren (WHO HBSC) survey.
  
  
  METHODS
  In the validity study, the Multistage Fitness Test was administered to a random sample of year 8 (mean age 13.1 years; n = 1072) and year 10 (mean age 15.1 years; n = 954) high school students from New South Wales (Australia) during February/March 1997. The students completed the self report instruments on the same day. An independent sample of year 8 (n = 121) and year 10 (n = 105) students was used in the reliability study. The questionnaire was administered to the same students on two occasions, two weeks apart, and test-retest reliability was assessed. Students were classified as either active or inadequately active on their combined responses to the questionnaire items. Kappa and percentage agreement were assessed for the questionnaire items and for a two category summary measure.
  
  
  RESULTS
  All groups of students (boys and girls in year 8 and year 10) classified as active (regardless of the measure) had significantly higher aerobic fitness than students classified as inadequately active. As a result of highly skewed binomial distributions, values of kappa were much lower than percentage agreement for test-retest reliability of the summary measure. For year 8 boys and girls, percentage agreement was 67% and 70% respectively, and for year 10 boys and girls percentage agreement was 85% and 70% respectively.
  
  
  CONCLUSIONS
  These brief self report questions on participation in vigorous intensity physical activity appear to have acceptable reliability and validity. These instruments need to be tested in other cultures to ensure that the findings are not specific to Australian students. Further refinement of the measures should be considered.
authors.affiliation: NSW Centre for the Advancement of Adolescent Health, Department of Paediatrics and Child Health, University of Sydney at The Children's Hospital at Westmead, New South Wales, Australia. michaeb4@chw.edu.au
authors.forename: M L
authors.initials: ML
authors.lastname: Booth
authors.forename: A D
authors.initials: AD
authors.lastname: Okely
authors.forename: T
authors.initials: T
authors.lastname: Chey
authors.forename: A
authors.initials: A
authors.lastname: Bauman
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D001315:Australia; D015444:Exercise; D005260:Female; D015438:Health Behavior; D006306:Health Surveys; D006801:Humans; D008297:Male; D010806:Physical Education and Training / Q000706:statistics & numerical data; D011153:Population; D011159:Population Surveillance; D015995:Prevalence; D015203:Reproducibility of Results; D017678:Sex Distribution; D013334:Students; D011795:Surveys and Questionnaires / Q000592:standards*; D013997:Time Factors; D014944:World Health Organization