| Authors | Country & Setting | Study design | Sampling technique & sample size | Method of analysis |
| Arillo-santillan E et al. 2005 [2] | Mexico, Public schools from 98 - 99 | Cross-sectional 1998-99 | systematic random sampling 5825 boys 7468 girls | Multinominal model, Multivariate logistic regression stratified by school levels, Multilevel model |
| Bidstrup PE et al. 2008 [15] | Denmark, 118 Public schools 230 classes, 2 classes per school with 13 pupils per class | Cross-sectional 2004 | Random sampling of schools (Data derived from Danish national institute of Public health in 2008) 1426 boys 1487 girls | Multilevel logistic regression |
| Bird Yet al. 2006 [9] | Juancz, Mexico, 6 Public & private schools. Data Collection year was not mentioned. | Cross-sectional study | Random sampling stratified by SES to select schools. All 6th grade students were selected 242 boys 264 girls | Multiple logistic regression by SES, school setting & gender |
| Bird Y et al. 2007 [16] | Ciudad Juarez, Mexico,6 Public & private schools in 2000 | Cross-sectional study | Random sampling stratified by SES to select schools. All 6th grade students were selected 242 boys 264 girls | Chi-squared test, ANOVA and logistic regression |
| Bond L et al. 2007 [17] | Victoria, Australia, 26 Secondary schools. Year of data collection not mentioned. | Longitudinal study | Data derived from Gatehouse project 1124 boys 1276 girls | Prevalence estimates, & Logistic regression using robust” “information sandwich” estimates of standard errors to account for clustering within schools. |
| Carson NJ et al. 2005 [18] | Northern Virginia Philadelphia, USA, 5 Public high schools. Year of data collection not mentioned | Cross-sectional | Data derived from another Longitudinal study of behavioural predictors of smoking. 967 adolescents | SEM, EFA, CFA, model fit assessed |
| Chang F et al. 2006 [19] | Taipei, Taiwan, 16 Vocational high schools 39 classes from 2000-2002 | Longitudinal study 3 years | Probability proportionate to size systematic random sampling to draw schools and classes. All 10th grade students selected 1695 boys and girls | GEE |
| Cleveland MJ et al. 2008 [20] | Pennsylvania, USA, 180 Public & private schools. from 2005 Pennsylvania Youth survey | Cross-sectional. | Random sampling stratified by 6 regions 91,778 boys and girls | Generalized linear mixed models, cumulative logit models (proportional odds model) |
| Conti DV et al. 2006 [21] | China, 62 Middle schools 83 Upper schools from Oct 2002-Dec 03 | Longitudinal study | Multistage cluster sampling stratified by school type 5042 boys 5606 girls | Multilevel random coefficient modeling |
| Damianaki A et al. 2008 [22] | Semi urban area in Crete, Greece, 15 Public schools from 2004-05 | Cross-sectional | Random sampling stratified by rural/urban status to select schools and students 386 boys 507 girls | Stepwise logistic regression, Mann-Whitney, t-test |
| Difranza JR et al. 2008 [23] | Urban and suburban region in central Massachusetts, USA, 2 Schools in 2007 | Cross-sectional | Convenience sampling 1055 boys and girls | 2-tailed Kendall’s tau b test for correlations |
| Ditre JW et al. 2008 [24] | Florida, USA, 3 High schools in 1999 | Cross-sectional | Convenience sampling 363 boys 394 girls | Mann-Whitney test, Kruskal Wallis, ANCOVA |