Table III.
Demographic characteristics of younger and older subsamples
| Younger (s.d.) | Older (s.d.) | Differences | |
|---|---|---|---|
| Groups | P = 0.59 | ||
| MZ | 134 | 80 | |
| DZ | 62 | 32 | |
| Siblings | 36 | 29 | |
| Singletons | 143 | 84 | |
| Age | 8.88 (2.00) | 14.72 (0.82) | P < 0.0001 |
| Sex | P = 0.10 | ||
| Male | 198 | 91 | |
| Female | 177 | 135 | |
| Ethnicity | P = 0.67 | ||
| White | 333 | 197 | |
| Black | 26 | 16 | |
| Asian | 6 | 4 | |
| Mixed | 10 | 8 | |
| Unknown | 0 | 1 | |
| Handedness | P = 0.82 | ||
| Right | 322 | 192 | |
| Mixed | 21 | 15 | |
| Left | 22 | 15 | |
| Unknown | 10 | 4 | |
| SESa | 42.63 (18.54) | 40.93 (18.39) | P = 0.29 |
| Mean cortical thicknessb | 4.17 (.38) | 4.11 (.31) | P = 0.03 |
Total number of younger subsamples is 375, and the total number of older subsamples is 226.
a
Socioeconomic status (SES) assessed using the Hollingshead scale(Hollingshead and Redlich, 1958), which ranges from 20 (highest SES) to 134 (lowest SES).
b
Unequal variances between groups; results are reported using one‐way ANOVA for consistency; Welch ANOVA provides a similar outcome.