Table 4.

Internal consistency of ODI (Cronbach’s alpha), n = 1,515

Item		n	Sign	Item-test correlation	Item-rest correlation	Average interitem covariance	Alpha
Item 1	Pain intensity	1515	+	0.66	0.58	0.67	0.86
Item 2	Personal care	1515	+	0.74	0.68	0.65	0.85
Item 3	Lifting	1515	+	0.70	0.62	0.65	0.85
Item 4	Walking	1515	+	0.61	0.50	0.68	0.86
Item 5	Sitting	1515	+	0.62	0.52	0.68	0.86
Item 6	Standing	1515	+	0.59	0.49	0.68	0.86
Item 7	Sleeping	1515	+	0.59	0.50	0.70	0.86
Item 8	Sex life	1515	+	0.75	0.63	0.59	0.86
Item 9	Social life	1515	+	0.76	0.68	0.63	0.85
Item 10	Travelling	1515	+	0.78	0.71	0.62	0.85
Total score						0.65	0.87a

^a95% CI 0.86 to 0.88