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Table 1 Traditional psychometric propertiesa

From: Patient Uncertainty Questionnaire-Rheumatology (PUQ-R): development and validation of a new patient-reported outcome instrument for systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) in a mixed methods study

Property Definition Criteria
Acceptability: Data quality The extent to which total scores can be computed – data completeness • Item level missing data <10 %,
• scale level missing data <50 %
Acceptability: Targeting The extent to which the range of uncertainty measured by the scale matches the range of uncertainty in the study sample • floor & ceiling effects <15 %
• skewness statistic range: -1 to 1
• precision of scores and means to scale possible scores & mid-points
Scaling assumptions The extent to which it is legitimate to sum a set of items, without weighting or standardization to produce a single total score. Summing PUQ-R scores is considered legitimate when (i) items are measured at the same point on the scale (ii) contribute similarly to the variation of the total score; (iii) measure a common underlying construct and (iv) contain similar proportion of information with regard to the construct being measured. • CITCs ≥0.30
• mean IIC ≥0.30
• ITCs ≥0.30
• item mean scores & standard deviations
Reliability The extent to which a scale scores are not associated with random error. Scale precision is based on homogeneity of items at a single point in time. • Cronbach’ s alpha ≥0.7
• homogeneity coefficient
• ITCs ≥0.30
Validity The extent to which a scale measures what it intends to measure. The extent to which a scale measures a single construct was assessed through internal consistency. Item convergent and discriminant validity with an item-total scale correlation criterion of >0.30 for the items’ own scale and a magnitude of > 2 standard errors than other scales. • Cronbach’s alpha ≥0.70
• ITC between item and own scale: 0.30 - 0.70
• ITC between item and other scale: >2 standard errors of ITC with own scale.
  1. CITC corrected item total correlation, IIC item-item correlation, ITC item total correlation
  2. aPsychometric properties are adapted from and explained in more detail in Cano et al 2010 [66]