Table 3.
Descriptive statistics and adjusted mean differences (95% CI) in test scores between twins and singletons
| Singletons | Twins | Estimated coefficient* (95% CI) | ||||
|---|---|---|---|---|---|---|
| Mean (SD) | Median (IQR) | Mean (SD) | Median (IQR) | |||
| Chinese | 10.9 (2.0) | 11 (10-12) | 10.8 (2.0) | 11 (10-12) | −0.108 (−0.202 to −0.014) | |
| English | 9.1 (3.2) | 9 (6-12) | 9.1 (3.3) | 9 (6-12) | 0.002 (−0.149 to 0.154) | |
| Mathematics | 6.9 (3.4) | 7 (4-9) | 6.7 (3.4) | 6 (4-9) | −0.168 (−0.326 to −0.010) | |
| Natural science | 10.0 (2.2) | 10 (8-12) | 9.8 (2.2) | 10 (8-11) | −0.174 (−0.277 to −0.070) | |
| Social science | 12.2 (1.7) | 12 (11-14) | 12.1 (1.8) | 12 (11-13) | −0.071 (−0.156 to −0.013) | |
| Overall test score | 49.1 (9.7) | 49 (42-56) | 48.5 (9.8) | 49 (41-56) | −0.528 (−0.928 to −0.075) | |
IQR=interquartile range.
*Adjusted for birth weight, gestation age, birth order, and sex and parents’ age, education, and work status at time of birth.