Means and standard deviations for ECLS-B measures of cognitive ability and achievement trajectories, for normal birth weight, HLBW, and LLBW children
| Normal birth weight (Greater than 2,500 grams) | HLBW (2,000–2,500 grams) | LLBW (Less than 2,000 grams) | |
|---|---|---|---|
| IQ or achievement measure | |||
| IQ at 24 months | 0.02 (1.00) | −0.17 (1.01) | −0.36 (0.96) |
| Number | 6,534 | 1,026 | 1,355 |
| PPVT 48 months | 0.02 (1.00) | −0.19 (0.98) | −0.24 (1.02) |
| 6,125 | 962 | 1,320 | |
| Reading 48 months | 0.02 (1.00) | −0.22 (0.91) | −0.13 (1.16) |
| 6,059 | 945 | 1,283 | |
| Math 48 months | 0.02 (1.00) | −0.27 (0.97) | −0.25 (1.04) |
| 6,059 | 940 | 1,267 | |
| Reading 60 months | 0.01 (1.00) | −0.13 (1.01) | −0.10 (1.00) |
| 4,941 | 715 | 1,032 | |
| Math 60 months | 0.02 (0.99) | −0.23 (1.02) | −0.25 (1.10) |
| 4,941 | 716 | 1,037 | |
| Demographic characteristics | |||
| Maternal education in years | 12.86 (2.86) | 12.63 (2.69) | 12.56 (2.77) |
| Number | 7,693 | 1,177 | 1,749 |
| Income / 180 percent poverty | 1.57 (1.45) | 1.33 (1.3) | 1.32 (1.3) |
| Number | 7,729 | 1,189 | 1,769 |
Note: Standard deviations are given in parentheses. All IQ scores are standardized based on the ECLS-B’s weighted national norms to have mean equal to 0 and standard deviation equal to 1.