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Table 4 Item scaling tests: convergent and discriminant validity for the QLQ PRT20 multi-item scales

From: International validation of the EORTC QLQ-PRT20 module for assessment of quality of life symptoms relating to radiation proctitis: a phase IV study

QLQ PRT20 Scales N items in scale Convergent validity (range of correlations) Discriminant validity (range of correlations) Scaling successesa Scaling success rateb Homogeneity (average inter-item r) Inter-item r > 0.3 & < 0.7 (%) Within scale Reliability (Cronbach’s α)
Bowel Control 4 0. 48–0.59 0.31–0.52 16/16 100% 0.431 100% 0.749
Bloating and Gas 4 0.48–0.66 0.25–0.46 13/16 81% 0.453 100% 0.767
Emotional Function/Lifestyle 5 0.56–0.76 0.26–0.56 19/20 95% 0.526 90% 0.843
Pain 3 0.40–0.67 0.17–0.53 11/12 92% 0.476 100% 0.732
Leakage 2 0.53 0.25–0.43 8/8 100% 0.530 100% 0.693
  1. a Number of convergent correlations significantly higher than the discriminant correlations/total number of correlations, b Scaling success rate scaling success as a percentage