Evaluation and validation of a patient-reported quality-of-life questionnaire for Parkinson’s disease

Journal of Patient-Reported Outcomes

Table 2 Results for reliability analysis for PDQoL7 and PDQ-8

PDQoL7 items	Inter-item correlations							Item-total correlation	Cronbach’s α if item deleted
PDQoL7 items	Item 1	Item 2	Item 3	Item 4	Item 5	Item 6	Item 7	Item-total correlation	Cronbach’s α if item deleted
PDQoL7
Item 1	–	0.748^**	0.281^*	0.530^**	0.324^*	0.345^**	0.163	0.604	0.767
Item 2	0.748^**	–	0.289^*	0.467^**	0.284^*	0.480^**	0.310^*	0.634	0.760
Item 3	0.281^*	0.289^*	–	0.452^**	0.544^**	0.433^**	0.086	0.511	0.784
Item 4	0.530^**	0.467^**	0.452^**	–	0.483^**	0.402^**	0.072	0.607	0.767
Item 5	0.324^*	0.284^*	0.544^**	0.483^**	–	0.353^*	0.299^*	0.552	0.776
Item 6	0.345^**	0.480^**	0.433^**	0.402^**	0.353^*	–	0.279	0.563	0.774
Item 7	0.163	0.310^*	0.086	0.072	0.299^*	0.279	–	0.285	0.815

PDQ-8 items	Inter-item correlations								Item-total correlation	Cronbach’s α if item deleted
PDQ-8 items	Item 1	Item 2	Item 3	Item 4	Item 5	Item 6	Item 7	Item 8	Item-total correlation	Cronbach’s α if item deleted
PDQ-8
Item 1	–	0.716^**	0.452^**	0.272^*	0.489^**	0.333^*	0.243	0.381^**	0.669	0.748
Item 2	0.716^**	–	0.406^**	0.297^*	0.514^**	0.225	0.375^**	0.449^**	0.702	0.742
Item 3	0.452^**	0.406^**	–	0.499^**	0.364^**	0.165	0.176	0.284^*	0.521	0.774
Item 4	0.272^*	0.297^*	0.499^**	–	0.202	0.566^**	− 0.075	0.397^**	0.455	0.784
Item 5	0.489^**	0.514^**	0.364^**	0.202	–	0.336^**	0.282^*	0.265^*	0.553	0.770
Item 6	0.333^*	0.225	0.165	0.566^**	0.336^**	–	0.047	0.456^**	0.451	0.785
Item 7	0.243	0.375^**	0.176	− 0.075	0.282^*	0.047	–	− 0.003	0.235	0.815
Item 8	0.381^**	0.449^**	0.284^*	0.397^**	0.265^*	0.456^**	− 0.003	–	0.483	0.780