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Table 2 Summary characteristics of outcome measures across the samples

From: Mapping the neck disability index to SF-6D in patients with chronic neck pain

Characteristic Whole set (n = 272) Derivation set (n = 180) Validation set (n = 92)
Mean (SD) Median (IQR) Mean (SD) Median (IQR) Mean (SD) Median (IQR)
SF-6D 0.52 (0.09) 0.49 (0.45-0.56) 0.53 (0.09) 0.49 (0.47-0.58) 0.5 (0.09) 0.48 (0.45-0.55)
NDI global scores 28.46 (12.93) 27 (18-40) 28.98 (13.87) 27.5 (18-43) 27.4 (10.97) 27 (18-34.75)
Scores of 10 individual items
 Pain intensity 3.47 (1.55) 3 (2-5) 3.52 (1.62) 3 (2-5) 3.37 (1.43) 3 (2-5)
 Personal care 2.14 (1.02) 2 (2-3) 2.17 (1.04) 2 (2-3) 2.1 (1) 2 (1.25-3)
 Lifting 2.63 (1.47) 2 (2-4) 2.7 (1.45) 2 (2-4) 2.5(1.5) 2 (1-3.75)
 Reading 3.08 (1.38) 3 (2-4) 3.12 (1.45) 3 (2-4) 3 (1.26) 3 (2-4)
 Headaches 2.67 (1.97) 2 (1-4) 2.68 (2.02) 2 (1-5) 2.63 (1.9) 2 (1-3.75)
 Concentration 2.94 (1.89) 2 (1-5) 3.02 (1.9) 2.5 (1-5) 2.8 (1.88) 2 (1-4)
 Work 2.74 (1.73) 2.5 (2-3) 2.77 (1.86) 2 (2-5) 2.7 (1.44) 3 (1.25-3)
 Driving 2.97 (1.88) 3 (2-5) 3.08 (1.94) 3 (2-5) 2.73 (1.74) 2.5 (2-4)
 Sleeping 2.58 (1.62) 2 (1-4) 2.72 (1.65) 2 (1-4) 2.3 (1.56) 2 (1-3.75)
 Recreation 3.23 (1.64) 3 (2-5) 3.22 (1.76) 3 (2-5) 3.27 (1.41) 3.5 (2-4)