Percentages and risk estimations of past 30-day smoking and low self-efficacya by parental migration among boys.

Variables adjusted included school, grade, ethnicity, perceived living standard (as a surrogate of family income) and gender and education of the guardian in the multivariate models.aSelf-efficacy was measured by the smoking self-efficacy questionnaire (SEQ-12), participants with scores below than the 25th percentile of all were defined as low self-efficacy.bRisks were estimated among all boys.cRisks were estimated among boys with paternal or maternal migration only.