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

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

PDQoL7 items Inter-item correlations Item-total correlation Cronbach’s α if item deleted
Item 1 Item 2 Item 3 Item 4 Item 5 Item 6 Item 7
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
Item 1 Item 2 Item 3 Item 4 Item 5 Item 6 Item 7 Item 8
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
  1. *P < 0.05; **P < 0.01