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Table 2 Test-retest reliability, measurement errors, Cronbach’s alpha and item-total correlation values for NDI-U (n = 46)

From: Urdu version of the neck disability index: a reliability and validity study

NDI-U Score 1st Measurement 2nd Measurement ICC (95% CI) SEM SDC Cronbach’s alpha Item-total correlation
Mean ± SD Mean ± SD
Question 1 2.09 ± 0.91 1.85 ± 0.87 0.86 (0.75–0.92) 0.32 0.89 NA 0.69
Question 2 0.91 ± 1.07 0.91 ± 1.05 0.98 (0.96–0.99) 0.15 0.42 NA 0.67
Question 3 2 ± 1.38 1.91 ± 1.31 0.96 (0.94–0.98) 0.27 0.75 NA 0.34
Question 4 1.78 ± 1.13 1.70 ± 1.13 0.97 (0.94–0.98) 0.19 0.53 NA 0.73
Question 5 1.50 ± 1.34 1.43 ± 1.31 0.98 (0.97–0.99) 0.19 0.53 NA 0.49
Question 6 1.39 ± 1.24 1.41 ± 1.20 0.98 (0.96–0.99) 0.17 0.47 NA 0.84
Question 7 1.30 ± 1.01 1.37 ± 1.06 0.95 (0.91–0.97) 0.23 0.64 NA 0.67
Question 8 1.45 ± 1.08 1.46 ± 1.07 0.93 (0.88–0.96) 0.28 0.78 NA 0.81
Question 9 1.26 ± 1.18 1.20 ± 1.09 0.96 (0.93–0.98) 0.22 0.61 NA 0.61
Question 10 1.50 ± 1.28 1.46 ± 1.33 0.97 (0.95–0.99) 0.22 0.61 NA 0.89
Total (0–50) 15.18 ± 8.58 14.70 ± 8.37 0.99 (0.98–0.99) 0.84 2.33 0.90 NA
  1. NDI-U Urdu version of the neck disability index, ICC Intra-class correlation coefficient, CI confidence interval, SEM Standard error of measurement, SDC Smallest detectable change, NA not applicable