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Table 2 Descriptive scale characteristics, factor structure, and reliability of the German version of the Neck Disability Index (NDI)

From: Validation of the German version of the Neck Disability Index (NDI)

Item Mean ± SD Item difficulty Factor loading Corrected item-total correlation Alpha if item deleted
Pain intensity 2.24 ± 0.77 0.45 0.57 0.44 0.80
Personal care 0.45 ± 0.63 0.09 0.67 0.54 0.80
Lifting 1.53 ± 1.12 0.31 0.56 0.42 0.80
Reading 2.07 ± 1.08 0.41 0.61 0.52 0.80
Headache 2.17 ± 1.38 0.43 0.48 0.38 0.81
Concentration 1.15 ± 1.04 0.23 0.71 0.59 0.78
Work 1.14 ± 1.00 0.23 0.76 0.63 0.78
Driving 2.05 ± 1.32 0.41 0.55 0.44 0.80
Sleeping 1.64 ± 1.26 0.33 0.59 0.47 0.79
Recreation 1.67 ± 0.86 0.33 0.75 0.64 0.78