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Table 1 Explanations of key psychometric concepts described in this paper

From: Psychometric properties of the expanded prostate cancer index composite - 26 instrument in a cohort of radical prostatectomy patients: theoretical and practical examinations

Explanatory factor analysis Statistical exploration of the underlying number of factors included in a questionnaire. The factor structure is the described by the number of factors, the items’ loading and the overall explained variance
Confirmatory factor analysis Statistical analysis testing whether the data fit a hypothesized measurement model of the questionnaire. Indicators of adequate model fit are given in the text.
Feasibility Indicates whether test persons find the questionnaire easy or complicated to complete.
Internal consistency Describes how well subscale items of the questionnaire go together, and eventually subscales in relation to the total questionnaire.
Criterion validity The questionnaire’s correlation with ‘gold standard’ questionnaires for the same concepts.
Convergent validity High correlations with other questionnaires covering the same concepts.
Divergent validity Low correlations with questionnaires covering other concepts.
Construct validity How well the questionnaire corresponds to other ways of measuring the construct i.e. various adverse effects.
Predictive validity The ability of the questionnaire score to predict important future outcome.
Responsiveness to change The ability of the questionnaire to identify clinical changes in the domains covered by the questionnaire.