Table 4 Psychometric evaluation

Internal consistency

We rated internal consistency as adequate when the Cronbach alpha was ≥0.7, not adequate when the criterion was not met and not applicable (NA) when internal consistency was not reported.

Reliability

We considered reliability as adequate when the Intraclass Correlation Coefficient (ICC) or weighted Kappa was ≥0.7, not adequate when the criterion was not met and not applicable (NA) when reliability was not reported.

Content validity

We considered content validity as adequate when the target population was involved in the development of the scale, not adequate when the criterion was not met and not applicable (NA) when the property was not reported.

Construct validity

Structural (factor analysis)

We rated construct validity as adequate when the factors explained at least 40% of the variance, not adequate when the criterion was not met and not applicable (NA) when construct validity was not reported.

Hypothesis testing

We rated construct validity as adequate when the correlation with an instrument measuring the same construct was ≥0.50 (OR at least 75% of the results were in accordance with the hypotheses) AND correlation with related constructs was higher than with unrelated constructs. Not adequate when the criterion was not met and not applicable (NA) when construct validity was not reported.

Criterion validity

We rated criterion validity as adequate when the correlation with a criterion instrument(s) was ≥0.50, not adequate when the criterion was not met and not applicable (NA) when criterion validity was not reported.

Measurement error

We rated measurement error as adequate when the Smallest Detectable Change (SDC) or Limit of Agreement (LoA) was less than Minimal Important Change (MIC), not adequate when the criterion was not met, and not applicable (NA) when measurement error was not reported.

Responsiveness

We rated responsiveness as adequate when the correlation with the anchor instrument was ≥0.50 (OR at least 75% of the results were in accordance with the hypotheses), not adequate when the criterion was not satisfied and not applicable (NA) when responsiveness was not reported.