Table 2.

Unidimensionality and Reliability after modification of the items in the Barthel Index (n = 644).

Variables	Original scale	Collapsing “mobility”	Removing “mobility”	Removing “stairs”	Combining “incontinence”	RC	RCC
Item Reliability	1.00	1.00	1.00	1.00	1.00	1.00	1.00
Person Reliability	0.88	0.88	0.88	0.88	0.88	0.88	0.87
Variance explained by Rasch dimension	72.9%	72.7%	74.7%	77.4%	74.1%	74.6%	75.6%
Variance explained by first contrast	6.6%	6.1%	5.2%	5.0%	6.4%	5.0%	4.7%
Eigenvalue of Rasch dimension	27.0	26.64	26.52	27.39	25.71	26.37	24.79
Eigenvalue of first contrast	2.4	2.21	1.84	1.78	2.21	1.80	1.53

Collapsing “mobility”, collapsing the second and the third categories of the “mobility” item; Removing “stairs”, removing the “stairs climbing” item; Combining “incontinence”, combining “controlling bowel” and “controlling bladder” into one item; RC, removing the “stairs climbing” item and collapsing the “mobility” item; RCC, removing the “stairs climbing” item, collapsing the “mobility” item, and combining “controlling bowel” and “controlling bladder” into one item. Values on the verge of meeting the requirements are marked in bold red.