Table 3.
Descriptive statistics of height and the covariates: Columns 1 and 2 show their mean and standard deviation. Columns 3–5 present the coefficients, standard error and p-value of the variables shown in the first column regressed on the instrument (a count of the number of height-increasing alleles).
| (1) Mean | (2) Std. dev. | (3) Coeff. | (4) Std. err. | (5) p-value | |
|---|---|---|---|---|---|
| Height (columns 1 and 2: in cm; columns 3–5: standardized) | |||||
| Age 8 | 132.2 | (5.6) | 0.430 | 0.081 | <0.001 |
| Age 13 | 163.3 | (7.6) | 0.474 | 0.089 | <0.001 |
| Control variables | |||||
| Age in months at Focus at 8 clinic | 103.1 | (2.21) | 0.018 | 0.017 | 0.284 |
| Age in months at Teen Focus 2 clinic | 166.0 | (2.12) | 0.011 | 0.015 | 0.466 |
| Age in months at KS3 exam | 169.6 | (3.76) | −0.033 | 0.025 | 0.194 |
| Birth weight (g) | 3422 | (549) | −1.505 | 3.699 | 0.684 |
| Younger siblings under 18 in the household | 0.51 | (0.65) | −0.003 | 0.004 | 0.543 |
| Older siblings under 18 in the household | 0.74 | (0.74) | 0.000 | 0.005 | 0.972 |
| Ln(income) | 5.32 | (0.45) | 0.000 | 0.003 | 0.995 |
| Father's education | 2.43 | (1.01) | 0.000 | 0.007 | 0.986 |
| Mother's education | 2.36 | (0.88) | 0.003 | 0.006 | 0.615 |
| Mother's mother's education | 1.73 | (0.75) | −0.001 | 0.005 | 0.829 |
| Mother's father's education | 1.84 | (0.79) | −0.003 | 0.005 | 0.610 |
| Child is not raised by natural father | 0.06 | (0.23) | 0.001 | 0.002 | 0.628 |
| Father's social class at the child's birth | 3.04 | (1.28) | −0.001 | 0.009 | 0.894 |
| Mother is employed part-time at 21 months | 0.40 | (0.49) | 0.008 | 0.003 | 0.020 |
| Mother is employed full-time at 21 months | 0.10 | (0.30) | −0.000 | 0.002 | 0.906 |
| Father is employed at 21 months | 0.92 | (0.28) | 0.004 | 0.002 | 0.038 |
| Index of Multiple Deprivation (IMD) | 19.50 | (13.95) | −0.014 | 0.100 | 0.891 |
| Mother: alcohol in month 1–3 of pregnancy | 0.57 | (0.50) | 0.004 | 0.003 | 0.266 |
| Mother: smoked in month 1–3 of pregnancy | 0.18 | (0.39) | −0.000 | 0.003 | 0.917 |
| Breastfeeding | 1.88 | (1.20) | 0.011 | 0.008 | 0.207 |
| Mother's age | 3.38 | (0.91) | 0.002 | 0.006 | 0.711 |
| Mother's ‘locus of control’ | 98.88 | (9.44) | −0.020 | 0.065 | 0.764 |
| Mother's EPDS | 6.46 | (4.54) | 0.025 | 0.031 | 0.412 |
| Mother's CCEI | 12.88 | (7.19) | 0.038 | 0.049 | 0.443 |
| Teaching score | 7.02 | (0.93) | 0.001 | 0.007 | 0.916 |
| Activities (indoor) score | 0.69 | (0.20) | 0.003 | 0.001 | 0.032 |
| Activities (outdoor) score | 27.89 | (4.61) | −0.008 | 0.032 | 0.810 |
Note: Rather than height in cm, the analysis uses standardized heights (with mean 100, standard deviation 10).