Motor function in Parkinson's disease and supranuclear palsy: simultaneous factor analysis of a clinical scale in several populations

Table 2 Model selection: Parkinson disease only: PD-On-Group and PD-Off- Group

Model	Description	χ²	df	RMSEA	TLI	CFI	St.RMR	Comments
PD1	Six factors based on component solutions -no constraints across groups; correlated residuals Facial and Speech	1318	592	0.071	.92	.93	0.08	BASELINE MODEL with 95% confidence interval of RMSEA: 0.065 – 0.077
PD2	As PD1: Within a factor all loadings equal	1578	634	0.078	.90	.91	0.10	Outside interval. PD2; too simple
PD3	As PD1: Loadings PD-On = Loadings PD-Off	1377	613	0.071	.92	.93	0.07	Simpler model than PD2
PD4	As PD3: Also equal factor covariance matrices	1450	634	0.072	.92	.92	0.09	Preferred model: Very simple; easy interpretation;
PD5	As PD4: Also residual variances and residual covariances equal across groups	2497	674	0.100	.82	.83	0.13	Rejected: Oversimplification

Note: RMSEA = Root mean square residual, CFI = comparative fit index, TLI = Tucker-Lewis Index, St.RMR = standardised root mean residual correlation.