Table 1.
Current cigarette smoking prevalence according to the survey method.
| Survey | Method | Total (N = 1059) | Boys (N = 444) | Girls (N = 615) | |||
|---|---|---|---|---|---|---|---|
| N | % | N | % | N | % | ||
| First survey | Self-reported questionnaire | 84 | 7.9 | 73 | 16.4 | 11 | 1.8 |
| Second survey | Self-reported questionnaire (A) | 112 | 10.6 | 93 | 21.0 | 19 | 3.1 |
| Urine cotinine (B) a | 95 | 9.0 | 79 | 17.8 | 16 | 2.6 | |
| Combined method (A and/or B, Gold standard) |
120 | 11.3 | 97 | 21.9 | 23 | 3.7 | |
| Estimated prevalence b | 115 | 9.9 | 75.5 c | 20.0 | 27 c | 4.6 | |
a Cutoff value of urinary cotinine concentration: 50 ng/mL. b Estimated prevalence from the mode by asking following question: “How many students smoke in your classroom?” In case of a mode value that was 0 or extreme (ex. 13 in 10th grade girls), we selected the second most frequent value. In a case of two mode values, we applied the mean of the two mode values. Estimated smoking prevalence was calculated by dividing the sum of the estimated number of smoking classmates by the total number of the students in selected class (N = 1163). c Co-educational classes (N = 204) were excluded in calculation of the number and percentage of the estimated smokers. The number of the denominator in boys and girls was 378 and 581, respectively.