Table II.
Model fit comparisons within the full bivariate ACE model examining qualitative and quantitative sex differences.
| Model | Model Description | Estimated Parameters |
−2LL | df | AIC | Δ(−2LL) | Δdf | p | Comparison Model |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Sex limitation, qual. on A and quant. sex-differences | 25 | 28985.38 | 10940 | 7105.38 | NA | NA | NA | NA |
| 2 | Sex limitation, qual. on C and quant. sex-differences | 25 | 28986.23 | 10940 | 7106.23 | 0.85 | 0 | NA | 1 |
| 3 | Scalar sex limitation, quant. sex-differences | 20 | 28986.93 | 10945 | 7096.93 | 1.55 | 5 | 0.91 | 1 |
| 4 | Homogeneity, no qual. nor quant. sex-differences | 13 | 29003.10 | 10952 | 7099.10 | 17.72 | 12 | 0.12 | 1 |
| 4 | Homogeneity, no qual. nor quant. sex-differences | 13 | 29003.10 | 10952 | 7099.10 | 16.17 | 7 | 0.02 | 3 |
Note: Models 1-4 include common paths for correlated factors a, c, and e. A=Additive genetic component, C=Common/Shared environmental component, E=Unique environmental component, qual.=qualitative, quant.=quantitative. Best fitting model is designated in bold text. All five twin groups are included in the modeling (MZ female, MZ male, DZ female, DZ male, DZ opposite sex). Best fitting model denoted in bold.