Table 3

 Sociodemographic and smoking differences between those providing full smoking data and those absent for one or more years, percentage/mean (n)

Full dataIncomplete dataSignificance
Sex
    Boys56.4 (1151)60.4 (2308)p = 0.003
    Girls43.6 (890)39.6 (1513)
Deprivation (mean score)2.9 (2037)3.2 (3599)p<0.001
Ethnicity
    White64.1 (1309)55.0 (2015)p<0.001
    Black22.6 (461)27.9 (1021)
    Asian11.1 (227)10.9 (400)
    Other2.2 (44)6.2 (227)
Conduct problems (mean score)2.6 (2034)3.0 (2252)p<0.001
Parental smoking
    Neither smoke62.5 (1274)46.6 (1049)p<0.001
    Father smokes18.5 (378)21.0 (472)
    Mother smokes8.6 (176)12.4 (279)
    Both smoke10.3 (210)20.0 (450)
Smoking
    Year 7 one time trier12.7 (260)20.7 (462)p<0.001
    Year 8 current smoker5.1 (105)11.4 (256)p<0.001
    Year 9 current smoker12.5 (255)18.4 (387)p<0.001
    Year 10 current smoker23.0 (469)26.3 (551)p = 0.013
    Year 11 current smoker29.3 (597)33.6 (562)p = 0.004