Table 2.
Comparison of RDD Controls, BC Controls, and US Births for Continuous Variables, Children's Oncology Group, 1995–2006a
| Variable | RDD Controls (n = 255) |
BC Controls (n = 70) |
RDD vs. BC P Value | Combined Controls (n = 325) |
US Population Estimate | |||
| Estimate | 95% Confidence Interval | Estimate | 95% Confidence Interval | Estimate | 95% Confidence Interval | |||
| Maternal age, years | ||||||||
| Mean | 30.02b | 29.3, 30.7 | 29.12b | 28.0, 30.3 | 0.22 | 29.83b | 29.2, 30.4 | 27.18 |
| Medianc | 29.58b | 28.8, 30.6 | 29.00b | 27.3, 30.0 | 29.50b | 28.9, 30.3 | 27 | |
| Maternal weight gain, poundsd | ||||||||
| Mean | 32.10 | 30.0, 34.2 | 31.94 | 27.9, 36.0 | 0.95 | 32.06 | 30.2, 33.9 | 30.98 |
| Medianc | 30.00 | 28.0, 33.0 | 31.50 | 25.0, 35.0 | 30.00 | 28.0, 33.0 | 30 | |
| Birth weight, g | ||||||||
| Mean | 3,446.63b | 3,374.5, 3,518.8 | 3,395.06 | 3,248.2, 3,541.9 | 0.52 | 3,435.52b | 3,371.0, 3,500.0 | 3,316.58 |
| Medianc | 3,458.64b | 3,402.0, 3,544.0 | 3,430.29 | 3,289.0, 3,515.0 | 3,458.64b | 3,402.0, 3,515.0 | 3,350 | |
Abbreviations: BC, birth certificate; RDD, random digit dialing.
a
For maternal age, the numbers of RDD controls, BC controls, and combined controls were 255, 69, and 324, respectively. For maternal weight gain and birth weight, the respective numbers were identical, that is, 255, 70, and 325.
b
The 95% confidence interval does not contain the US population estimate.
c
Based on a bootstrap confidence interval using the method of adjusted bootstrap percentile except where unstable, when the percentile method was used.
d
One pound = 0.45 kg.