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Table 5 Thresholds for the PHQ-15 based on IRT analysis

From: Validation of the Chinese version of the PHQ-15 in a tertiary hospital

  Diff. Coef. Std. Err. z P > z [95 % Conf. Interval]
Item 1 1 vs 0 0.994 0.069 14.44 <0.001 0.859 1.129
  2 vs 1 2.132 0.124 17.13 <0.001 1.888 2.376
Item 2 1 vs 0 0.355 0.061 5.76 <0.001 0.235 0.476
  2 vs 1 2.024 0.108 18.75 <0.001 1.812 2.235
Item 3 1 vs 0 0.326 0.063 5.19 <0.001 0.203 0.448
  2 vs 1 1.532 0.091 16.83 <0.001 1.354 1.710
Item 4 1 vs 0 2.498 0.114 21.89 <0.001 2.274 2.721
  2 vs 1 2.583 0.228 11.34 <0.001 2.136 3.029
Item 5 1 vs 0 0.780 0.065 12.00 <0.001 0.652 0.907
  2 vs 1 2.472 0.137 18.10 <0.001 2.204 2.740
Item 6 1 vs 0 0.725 0.064 11.24 <0.001 0.598 0.851
  2 vs 1 2.338 0.128 18.22 <0.001 2.087 2.590
Item 7 1 vs 0 0.387 0.061 6.35 <0.001 0.268 0.506
  2 vs 1 2.587 0.135 19.17 <0.001 2.323 2.852
Item 8 1 vs 0 1.849 0.090 20.57 <0.001 1.673 2.025
  2 vs 1 2.187 0.157 13.96 <0.001 1.880 2.494
Item 9 1 vs 0 0.597 0.063 9.49 <0.001 0.474 0.720
  2 vs 1 2.389 0.128 18.62 <0.001 2.138 2.641
Item 10 1 vs 0 0.928 0.068 13.60 <0.001 0.794 1.062
  2 vs 1 1.914 0.114 16.85 <0.001 1.691 2.137
Item 11 1 vs 0 1.792 0.088 20.35 <0.001 1.619 1.964
  2 vs 1 2.202 0.155 14.21 <0.001 1.898 2.505
Item 12 1 vs 0 0.172 0.061 2.81 0.005 .0519 0.292
  2 vs 1 1.840 0.099 18.61 <0.001 1.646 2.033
Item 13 1 vs 0 0.203 0.061 3.32 0.001 0.083 0.323
  2 vs 1 1.942 0.103 18.88 <0.001 1.741 2.144
Item 14 1 vs 0 −0.485 0.067 −7.60 <0.001 −0.610 −0.360
  2 vs 1 1.719 0.090 19.23 <0.001 1.544 1.894
Item 15 1 vs 0 −0.843 0.062 −1.35 0.177 −0.207 0.038
  2 vs 1 1.403 0.084 16.79 <0.001 1.239 1.567
  1. Partial credit model, number of observations = 1329
  2. Log likelihood = −14252.727
  3. AIC = 28567.45
  4. BIC = 28728.41