Print Email Facebook Twitter Response conversion for improving comparability of international physical activity data Title Response conversion for improving comparability of international physical activity data Author Hopman-Rock, M. Dusseldorp, E. Chorus, A. Jacobusse, G. Ruetten, A. van Buuren, S. Publication year 2012 Abstract Background: Many questionnaires for measuring physical activity (PA) exist. This complicates the comparison of outcomes. Methods: In 8 European countries, PA was measured in random samples of 600 persons, using the IPAQ as a 'bridge' to historical sets of country-specific questions. We assume that a unidimensional scale of PA ability exists on which items and respondents can be placed, irrespective of country, culture, background factors, or measurement instrument. Response Conversion (RC) based on Item Response Theory (IRT) was used to estimate such a common PA scale, to compare PA levels between countries, and to create a conversion key. Comparisons were made with Eurobarometer (IPAQ) data. Results: Appropriateness of IRT was supported by the existence of a strong first dimension established by principal component analysis. The IRT analysis resulted in 1 common PA scale with a reasonable fit and face validity. However, evidence for cultural bias (Differential Item Functioning, DIF) was found in all IPAQ items. This result made actual comparison between countries difficult. Conclusions: Response Conversion can improve comparability in the field of PA. RC needs common items that are culturally unbiased. Wide-scale use of RC awaits measures that are more culturally invariant (such as international accelerometer data). © 2012 Human Kinetics, Inc. Subject HumanCH - Child HealthBSS - Behavioural and Societal SciencesHealthHealthy LivingCultural biasDifferential item functioningIPAQItem response theory To reference this document use: http://resolver.tudelft.nl/uuid:5d7f0f46-a1a3-48cf-93b7-c6cc409b9198 TNO identifier 446411 ISSN 1543-3080 Source Journal of Physical Activity and Health, 9 (1), 29-38 Document type article Files To receive the publication files, please send an e-mail request to TNO Library.