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Table 2 Prevalence of smoking by grade

From: Psychosocial factors associated with smoking and drinking among Japanese early adolescent boys and girls: Cross-sectional study

  None 1–2 times Sometimes Once a week More than 2–3 times a week  
  N (%) N (%) N (%) N (%) N (%)  
Totala 2713 (93.5) 84 (2.9) 66 (2.3) 7 (0.2) 32 (1.1)  
Boys 1350 (92.1) 47 (3.2) 41 (2.8) 4 (0.3) 24 (1.6) **b
Girls 1363 (94.9) 37 (2.6) 25 (1.7) 3 (0.2) 8 (0.6)  
Gradea            **d
   7th 843 (95.9) 18 (2.0) 15 (1.7) 2 (0.2) 1 (0.1)  
Boys 426 (95.7) 9 (2.0) 8 (1.8) 1 (0.2) 1 (0.2)  
Girls 417 (96.1) 9 (2.1) 7 (1.6) 1 (0.2) 0 (0)  
   8th 935 (92.9) 35 (3.5) 21 (2.1) 4 (0.4) 12 (1.2) **e
Boys 449 (90.5) 20 (4.0) 14 (2.8) 3 (0.6) 10 (2.0) *c
Girls 486 (95.1) 15 (2.9) 7 (1.4) 1 (0.2) 2 (0.4)  
   9th 935 (92.0) 31 (3.1) 30 (3.0) 1 (0.1) 19 (1.9) ***f
Boys 475 (90.5) 18 (3.4) 19 (3.6) 0 (0) 13 (2.5)  
Girls 460 (93.7) 13 (2.6) 11 (2.2) 1 (0.2) 6 (1.2)  
  1. Prevalence of tobacco use in the last six months among Japanese adolescent boys and girls by grade are shown.
  2. Significant at * p < 0.05; ** p < 0.01; *** p < 0.001 (two-tailed).
  3. a Does not total 2,923 due to missing data. (N = 2,902)
  4. b In the two-independent-sample tests by the Mann-Whitney U test among gender, the prevalence among boys was significantly higher than among girls.
  5. c In 8th graders, the prevalence among boys was significantly higher than among girls.
  6. d In the multiple comparison tests by the Kruskal Wallis test, there was significant difference among grades.
  7. e In the two-independent-sample tests by the Mann-Whitney U test between each of the two grades, the prevalence among 8th graders was higher than among 7th graders.
  8. f The prevalence among 9th graders was higher than among 7th graders.