Table 4 Absolute frequencies, outcome prevalences, exposure prevalences, crude and pooled prevalence ratio (PR) estimates, and relative confounding for the analysis of the modified data using asthma as the outcome, maternal smoking as the risk factor and social class as confounder (situation 2 modified).
First stratum: High social class | |||||
|---|---|---|---|---|---|
Asthma | No | All | |||
N | Prev. | N | N | Exp. prev. = 26.6% | |
Mother smokes | 21 | 14.6% | 123 | 144 | PR = 1.21 |
No | 48 | 12.1% | 350 | 398 | M-H weight = 12.75 |
All | 69 | 12.7% | 473 | 542 | |
Second stratum: Low social class | |||||
Asthma | No | All | |||
N | Prev. | N | N | Exp. prev. = 43.3% | |
Mother smokes | 194 | 68.1% | 91 | 285 | PR = 1.70 |
No | 149 | 39.9% | 224 | 373 | M-H weight = 64.54 |
All | 343 | 52.1% | 315 | 658 | |
Combined strata: High and low social class | |||||
Asthma | No | All | Exp. prev. = 35.8% | ||
N | Prev. | N | N | PR (crude) = 1.96 | |
Mother smokes | 215 | 50.1% | 214 | 429 | PR (M-H) = 1.62 |
No | 197 | 25.6% | 574 | 771 | Confounding = -17.3% |
All | 412 | 34.3% | 788 | 1200 | P-value(het)*= 0.2 |