Table 1.

Summary of tests and criteria

Property	Definition/test	Criteria for acceptability
Item performance	Data quality; assessed by completeness of data and score distributions Frequency and percentage of missing data per item Floor/ceiling effects Response option frequencies	Items missing in more than 10% of responses Ceiling effect: % of responses in the highest response category > (100/the number of response options on an item) %, eg, 20% for a five-response ordinal scale Floor effect: % of responses in the lowest response category > (100/the number of response options on an item) %, eg, 20% for a five-response ordinal scale Utilization of all response options
Reliability	Internal consistency reliability: extent to which items in a domain measure the same concept; assessed by Cronbach’s α and inter-item correlations assessed by Spearman’s or Pearson’s coefficient	Cronbach’s α≥0.70 was considered to indicate internal reliability Inter-item correlation (Pearson or Spearman coefficient items of r>0.80 should be highlighted as potentially redundant)
Validity (hypothesis testing)	Evidence that the questionnaire measures a single concept, that items can be combined to form a summary score, and that domains measure distinct but related concepts Concurrent validity: hypotheses based on criterion measure(s) Known groups differences: ability of a scale to differentiate among known groups	Concurrent validity: Spearman’s coefficient values of <0.3, 0.31–0.59, and >0.6 were considered to indicate low, moderate, and high levels of correlation, respectively, with acceptable ranges for convergence identified at ≥0.4