Table 1.
Means and standard deviations by sex and zygosity
| Sex | Zygosity | Sex * Zygosity | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
|||||||||||||
|
Girls
M (SD) |
Boys
M (SD) |
F | P | μ 2 |
MZ
M (SD) |
DZ
M (SD) |
F | P | μ 2 | F | p | μ 2 | |
| Vocabulary | .01 | .01 | .04 | .84 | .000 | −.04 | .03 | 4.59 | .03 | .001 | 1.30 | .25 | .000 |
| (1.01) | (.99) | (1.02) | (.99) | ||||||||||
| Listening | .03 | −.06 | 8.29 | .00 | .002 | −.05 | .01 | 4.54 | .03 | .001 | .24 | .62 | .000 |
| Grammar | (1.00) | (.99) | (.99) | (1.00) | |||||||||
| Making | .06 | −.04 | 8.46 | .00 | .002 | .00 | .02 | 1.58 | .21 | .000 | .61 | .44 | .000 |
| Inferences | (.99) | (1.02) | (1.00) | (1.01) | |||||||||
| Figurative | .00 | .03 | .81 | .84 | .000 | −.01 | .03 | 1.58 | .21 | .000 | .64 | .42 | .000 |
| Language | (.99) | (.99) | (.99) | (.99) | |||||||||
Note: M = mean; SD = standard deviation; MZ = monozygotic twins; DZ = dizygotic twins; F, p, and μ2 derived from MANOVA performed using one member of each twin pair (total N = 4319; 925 MZ girls, 1476 DZ girls, 659 MZ boys, 1259 DZ boys).
Manova
Intercept: F (4, 4312) = 1.39, p = .24
Sex: F = (4, 4312) = 5.86, p < .00
Zygosity: F = (4, 4312) = 1.75, p = .137
Sex * zygosity: F = (4, 4312) = .362, p = .00