Rasch analysis of the Hospital Anxiety and Depression Scale (HADS) for use in motor neurone disease

Table 2 Summary Fit Statistics for Rasch Analyses

	# of items	Item Residual		Person Residual		Chi Square		PSI	Unidimensional t-test (CI %)	Extreme scores (%)
Analysis Name		Mean	± SD	Mean	± SD	Value	p
HADS-D Initial	7	-0.19	1.51	-0.32	0.77	59.76	< 0.01	0.80	5.17% (2-7%)	0.30%
HADS-D Final	6	-0.15	1.30	-0.30	0.81	39.90	0.20	0.79	4.74% (2.4-8.1%)	15.11%
HADS-A Initial	7	0.14	2.09	-0.30	1.08	52.27	< 0.01	0.92	4.44% (2-7%)	1.70%
HADS-A Final	6	0.00	1.50	-0.36	1.01	34.75	0.07	0.84	5.07% (3-8%)	2.34%
HADS-T Initial	12	0.01	1.45	-0.21	0.90	113.92	< 0.01	0.86	9.90% (6-14%)	1.80%
HADS-T Final	10	-0.02	2.02	-0.47	0.87	10.51	0.23	0.76	7.37% (4-10%)	4.03%
*Ideal Values*		0	< 1.4*	0	*< 1.4*		*> 0.05* ^a	*> 0.85*	*< 5% (CI < 0.05)*

Key: SD- Standard Deviation, p - Probability, PSI - Person Separation Index, CI - Confidence Interval
*= Can be inflated in the presence of testlets to accommodate local dependence.

ISSN: 1477-7525