Table 1.
NCS-A sample disposition
| Household | Un-blinded School | Blinded School | Total | |||||
|---|---|---|---|---|---|---|---|---|
| % | (n) | % | (n) | % | (n) | % | (n) | |
| I. Adolescents | ||||||||
| Interview | 85.9 | (904)a | 81.8 | (8,912) | 22.3 | (332) | 75.6 | (10,148) |
| Refusalb | 11.3 | (119) | 14.7 | (1,604) | 76.4 | (1137) | 21.3 | (2,860) |
| Circumstantial | 2.4 | (25) | 1.9 | (211) | 2.9 | (13) | 1.9 | (249) |
| No contact | 0.4 | (4) | 1.5 | (165) | 0.4 | (6) | 1.3 | (175) |
| II. Parents | ||||||||
| Full questionnaire | 52.4 | (551)c | 52.4 | (5,703) | 15.9 | (237) | 48.3 | (6,491) |
| Short-form questionnaire | 18.5 | (195)c | 16.0 | (1,744) | 3.7 | (55) | 14.8 | (1,994) |
| Either | 70.9 | (746) | 68.4 | (7,447) | 19.6 | (292) | 63.0 | (8,485) |
| (n) | (1,052) | (10,892) | (1,488) | (13,432) | ||||
25 of the household survey respondents were not students. The remaining 879 were students.
The much higher refusal rate in the blinded school sample than the other samples was due to the fact that in blinded schools active written parental consent, in the form of a signed return postcard in response to a letter mailed by the school Principal, was required before the school would release the names and addresses of sample adolescents to the research team. Some 74.9% of parents in blinded schools failed to return these postcards, while another 1.5% of cases were omitted because of refusal on the part of either the parent (0.9%) or the adolescent (0.6%).to participate after a parent had signed the informed consent postcard. As in the blinded school sample, the majority of refusals in both the household sample (72.3%) and the unblended school sample (81.0%) came from parents rather than adolescents.
15 of the parents who completed a questionnaire (8 full questionnaire, 7 short-form questionnaire) were the parents of adolescents who were not students.