Table 1.
Descriptive statistics for control variables, the intelligence scores of the IDS, RIAS, SON-R 6-40, WISC-IV, and school grades in study waves 1 and 2.
| Variable | Study wave 1 (N = 103) | Study wave 2 (N = 54) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Mean (SD) | N (%) | Range | Skewness | Kurtosis | Mean (SD) | N (%) | Range | Skewness | Kurtosis | |
| Sex | ||||||||||
| Female | 54 (52) | 28 (52) | ||||||||
| Male | 49 (48) | 26 (48) | ||||||||
| Age at Study wave 1 (years) | 9.18 (0.93) | 6.71–11.18 | −0.19 | 0.26 | 9.04 (0.96) | 6.71–11.18 | −0.08 | −0.14 | ||
| Age at Study wave 2 (years) | 11.77 (0.80) | 10.25–13.60 | 0.43 | −0.51 | ||||||
| Parental education | ||||||||||
| Non-tertiary education | 74 (72) | 40 (74) | ||||||||
| Tertiary education | 29 (28) | 14 (26) | ||||||||
| IDS | 103.54 (10.64) | 78–134 | 0.15 | 0.41 | 105.19 (10.74) | 79–134 | 0.45 | 0.70 | ||
| RIAS | 101.45 (8.99) | 81–128 | 0.29 | 0.39 | 103.65 (8.23) | 87–128 | 0.84 | 0.67 | ||
| SON-R 6-40 | 103.27 (11.32) | 79–139 | 0.38 | 0.50 | 103.67 (11.55) | 82–139 | 0.62 | 0.61 | ||
| WISC-IV | 104.88 (11.91) | 73–133 | 0.21 | 0.07 | 107.39 (10.58) | 84–133 | 0.27 | 0.28 | ||
| Averaged school grade | 5.16 (0.42) | 4–6 | −0.39 | −0.20 | ||||||
| Mathematics school grade | 5.15 (0.48) | 4–6 | −0.25 | −0.71 | ||||||
| Language school grade | 5.16 (0.43) | 4–6 | −0.31 | −0.08 | ||||||
IDS, Intelligence and Development Scales; RIAS, Reynolds Intellectual Assessment Scales; SON-R 6-40, Snijders-Oomen Nonverbal Intelligence Test Revised; WISC-IV, Wechsler Intelligence Scale for Children—Fourth Edition.