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. Author manuscript; available in PMC: 2013 Jul 23.
Published in final edited form as: Thorax. 2011 Aug 25;66(10):875–883. doi: 10.1136/thoraxjnl-2011-200489

APPENDIX 1.

Study sample details

Germany Iceland Italy Poland The Netherlands UK
Setting Public schools, 4 school types: Gymnasium, Gemeinschaftsschule, Regional schule, Hauptschule Public schools Public schools, 2nd class of secondary school and 1st class of high school Public schools, 1 school type (Gymnasium) Public schools, 4 different school types: VMBO, HAVO, Atheneum, Gymnasium Mainstream (state-funded) schools
Locations Schleswig-Holstein, Germany District of Kiel, Flensburg, Schleswig-Flensburg, and Rendsburg-Eckernförde Schools from each region (north, south, east and west) of Iceland in addition to the capital area (Reykjavík and surrounding municipalities) Piedmont region, Italy schools with head office in Turin and Novara provinces Wielkopolska region Gelderland, Limburg, Brabant Central belt of Scotland
Time of data assessment Nov–Dec 2009 Jan–Feb 2010 March–June 2010 April–June 2010 Dec 2009–June 2010 Jan–Mar 2010
Eligibility criteria for schools Location Number of classes >8 No special pedagogic education centre No participation in other studies of IFT-Nord Number of participating students >100 Location in Turin and Novara provinces Location in Wielkopolska region No special pedagogic education centre No special pedagogic education centre No current participation in other studies of the Behavioural Science Institute, Radboud University Location in either Midlothian or East Dumbartonshire Not providing special education Not providing private (non-state-funded) education
No. of schools potentially eligible n=104 Not known n=578 n=253 Not known n=14
No. of schools invited n=60 n=23 n=31 n=253 n=43 n=7
Invitation criteria for schools Random Convenience sampling Convenience sampling All eligible schools Random Selected on the basis of deprivation, based on the most recent (2007–2008) nationally available data relating to the proportion of free school meals
No. of schools that agreed to participate n=21 n=20 n=26 n=35 n=5 N=7
Eligibility criteria for students Active (`opt-in') parental consent Presence on the day of assessment or, if absent, willing to complete a questionnaire and return by post Willingness to participate Passive (`opt-out') parental consent Students' presence on the day of assessment Willingness to participate Active or passive parental consent Willingness to participate or, if absent, willing to complete a questionnaire and return by post Active (`opt-in') parental consent Presence on the day of assessment Willingness to participate Passive parental consent Presence on the day of assessment Willingness to participate Passive (`opt-out') parental consent Presence on the day of assessment or, if absent, willing to complete a questionnaire and return by post Willingness to participate
No. of students examined for eligibility n=3544 n=2798 n=2953 n=5078 n=1706 n=3189
Confirmed eligibility n=2754 n=2662 n=2668 n=4105 n=1423 n=2937
Reasons for non-participation No parental consent (n=515) Absence (n=264) Refusal (n=11) No parental consent (n=19) Absence (n=104) Refusal (n=13) No parental consent (n=100) Absence (n=175) Refusal (n=10) No parental consent (n=396) Absence (n=527) Refusal (n=50) No parental consent (n=18) Absence (n=265) Refusal (n=0) No parental consent (n=11) Absence (n=226) Refusal (n=15)
Participated in the study n=2754 n=2662 n=2668 n=4105 n=1423 n=2937
Analysed n=2754 n=2662 n=2668 n=4105 n=1423 n=2937
Response rate 78% 95% 90% 81% 83% 92%