Table 6.
Best-fitting liability threshold model results for categorical data on stuttering (unaffected /affected) by age.
| Models | Par | -2LL | df | LRT(df) | AIC |
|---|---|---|---|---|---|
| AGE 3 | |||||
| Saturated model | 15 | 2923.973 | 11132 | ||
| AE model equated across boys and girls | 4 (+ 2 constraints) | 2940.503 | 11145 | 16.53 (13) | -9.47 |
| AGE 4 | |||||
| Saturated model | 15 | 4237.520 | 14576 | ||
| AE model equated across boys and girls | 4 (+ 2 constraints) | 4257.588 | 14589 | 20.07 (13) | -5.93 |
| AGE 7 | |||||
| Saturated model | 15 | 2136.411 | 14091 | ||
| AE model equated across boys and girls | 4 (+ 2 constraints) | 2146.991 | 14104 | 10.58 (13) | -15.42 |
Abbreviations: Par = Parameters estimated in the model. -2LL = Log likelihood fit statistic. df = Degrees of freedom. LRT(df) = Likelihood ratio χ2 test with Δdf comparing reduced models to the full model. AIC = Aikaike’s information criteria (as computed by LRT - 2*df), the smaller the AIC the better the fit of the model. Nonsignificant p- values indicate a good model fit.
Note: Models tested were: ACE full sex limitation model allowing both qualitative and quantitative sex difference, ACE common effect submodel allowing only quantitative sex differences, ACE allowing no qualitative or quantitative sex differences, AE allowing no qualitative or quantitative sex differences and dropping the shared environment parameter, equivalent ADE models were also tested but did not lead to a better fit.