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Glossary of Psychometric Properties

 
Additional Information

Construct validity:

Refers to the extent to which results of the tool relate in a predictable manner to other measures of the concept being measured.

  • Convergent validity: Degree of association between two instruments measuring similar constructs.
  • Divergent validity: Difference in degree of association between instruments measuring different constructs.
  • Group differences: Ability of an instrument to identify differences in various known categories of subjects.
  • Predictive validity: Ability of an instrument to predict future events.

Criterion validity:

Evaluates how well the questionnaire compares to the gold standard.

Reproducibility or reliability:

Extent to which a questionnaire remains stable when a subject is re-tested either at different time points or by different evaluators.

  • Kappa: Fraction of agreement observed that is not related to chance.
  • Spearman’s rho: Used for ordinal or rank order measurements of correlation.
  • Intra-class correlation: Estimates the overall measurement variance of an instrument including both inter-individual variance and intra-individual variance.
  • Cronbach’s alpha: Measures internal consistency. Identifies the correlation among items in a scale.

Responsiveness and sensitivity:

Assesses the “ability of a questionnaire to detect clinically important changes over time”1.

  • Area under receiver operator curves (ROC-AUC): Receiver operator curves allow for the evaluation of an instrument using different cut-off points. They are constructed by plotting sensitivity against 1-specificity (one minus specificity). The area under the curve measures the instrument’s performance.
  • CART analysis: Classification and Regression Tree Analysis is a method of decision tree analysis.

References

  1. Terwee C.B., Bot S.D.M., de Boer M.R., van der Windt D.A.W.M, Knol D.L., Dekker J., Bouter L.M., de Vet H.C.W. Quality criteria were proposed for measurement properties of health status questionnaires. J Clin Epidemiol 2007 (60): 34-42.
  2. McDowell I. Measuring Health: A Guide to Rating Scales and Questionnaires. 3rd Edition. Oxford University Press. 2006.
  3. Sikorskii A, Noble P.C. Statistical considerations in the psychometric validation of outcome measures.Clin Orthop Relat Res 2013 (471): 3489-3495.