Validity and reliability of study questionnaires
| Questionnaire | Details | Validity/reliability |
| Self-efficacy (Self-Efficacy for Diabetes Self-Management Measure) | Participants will rate their degree of certainty in their ability to correctly carry out 10 diabetes management tasks on a 10-point Likert scale ranging from ‘not sure at all’ to ‘completely sure’. | The test-retest intraclass correlation for the measure was 0.89. The Cronbach’s alpha coefficient 0.90. |
| Diabetes knowledge (L'Aide aux Jeunes Diabétiques Diabetes Knowledge and Skills questionnaire) | A validated scale composed of 50 true-false questions | Construct validity: scores differed by haemoglobin A1c (p<0.001) and by age (p<0.001). |
| Transition readiness (Am I ON TRAC? For Adult Care questionnaire) | The questionnaire is a 25-item validated scale consisting of: (1) knowledge scale with a 4-point Likert scale ranging from ‘strongly disagree’ to ‘strongly agree’ and a (2) behaviour index with a 5-point ordinal scale, ‘never’ to ‘always’ and asks youth to report how frequently they engage in several health-related behaviours | Cronbach’s alpha coefficient 0.93 |
| Diabetes distress (Diabetes Distress Scale for Adults with Type 1 Diabetes) | A validated 28-item self-report scale | Alpha coefficient 0.91. The test-retest reliability was 0.74. |
| Quality of life (Paediatric Quality of Life Inventory Generic Core Scale and Diabetes Module) | A 23-item and 33-item questionnaire, age-specific for 13- to 18-year-olds will be used | Cronbach’s alpha coefficient 0.88 |