TABLE 3.

GOODNESS-OF-FIT STATISTICS FROM STRUCTURAL EQUATION MODELING OF CHRONIC BRONCHITIS

Model	−2log–likelihood	LRT*	P Value
1	15,540.658
2	15,541.315	0.657	0.418
3	15,543.867	2.552	0.466
4	15,543.867	0	0.500†
5	15,659.395	115.528	<0.001†

Models: (1) rg (genetic correlation) free for DZ OS (dizygotic opposite-sex twins), ACE different for males and females; (2) rg fixed at 0.5 for DZ OS, ACE different for males and females; (3) rg fixed at 0.5 for DZ OS, ACE same for males and females; (4) rg fixed at 0.5 for DZ OS, AE; (5) rg fixed at 0.5 for DZ OS, E.

^*Likelihood ratio test for comparing the model versus the proceeding model.

^†Accounting for the fact that a test of a variance component is a boundary problem.