Table 2 Mean (SD) values of knowledge and attitudes scores by exposure status and grade category as well as multiple linear regression derived estimates of the per cent of difference in mean scores due to exposure to messages.
| Variable | Grade category | Without exposure | After exposure | Adjusted* difference (%) | 95% CI (%) | p Value | ||
|---|---|---|---|---|---|---|---|---|
| Mean score (%) | SD (%) | Mean score (%) | SD (%) | |||||
| Knowledge | Kindergarten | 65.68 | 20.68 | 84.20 | 17.64 | 17.40 | 6.41 (28.39) | 0.005 |
| Elementary school | 61.93 | 20.26 | 75.79 | 20.64 | 14.58 | −3.05 (32.21) | 0.08 | |
| High school | 70.59 | 16.85 | 70.82 | 18.79 | −0.15 | −5.30 (4.99) | 0.92 | |
| p<0.001 | ||||||||
| Attitudes | Kindergarten | 58.66 | 36.13 | 77.39 | 32.61 | 23.64 | 4.48 (42.79) | 0.02 |
| Elementary school | 42.82 | 20.05 | 48.58 | 20.28 | 5.64 | −11.47 (22.77) | 0.41 | |
| High school | 31.04 | 26.22 | 37.20 | 25.41 | 6.32 | −1.87 (14.52) | 0.09 | |
| p = 0.01† | ||||||||
*Adjusted for age, gender, sibship size, maternal education and knowledge of swimming.
†Derived from the Wald test for heterogeneity of the underlying coefficients indicating the significance of the differential effect of the intervention by grade category.