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

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

QLQ PRT20 Scales	N items in scale	Convergent validity (range of correlations)	Discriminant validity (range of correlations)	Scaling successes^a	Scaling success rate^b	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

^a Number of convergent correlations significantly higher than the discriminant correlations/total number of correlations, ^b Scaling success rate scaling success as a percentage

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