title: [Reliability and validity of Comprehensive Work Ability Index scales].
abstract: OBJECTIVE
  To test the reliability and the validity of Comprehensive Work Ability Index (CWAI) scales.
  
  
  METHODS
  For evaluating the reliability and validity of CWAI scales, 1959 subjects employed in various kinds of occupations were selected with the random cluster sampling method. 245 subjects of them were retested at intervals of 2 to 4 weeks in order to assess the test-retest reliability. The sample for criterion validity consisted of 86 subjects. The inter-item consistency (Cronbach's alpha coefficient, Spearman-Brown coefficient, theta coefficient and Omega coefficient), test-retest reliability (intra-class correlation coefficient) and Pearson correlation were calculated to assess the reliability of CWAI scales. Pearson correlation analysis, and factor analysis were used to assess the validity of CWAI scales.
  
  
  RESULTS
  The reliability analysis showed that CWAI was significantly correlated with the item scores (P < 0.01), and most of the correlation coefficients were higher than 0.30. Generally speaking, Cronbach's alpha coefficients (ranging from 0.701 to 0.808), theta coefficient (ranging from 0.703 to 0.845) and Omega coefficient (ranging from 0.802 to 0.942) and Spearman-Brown coefficient (0.860) conformed to the requirements of psychometric study. The intra-class correlation coefficient (ranging from 0.597 to 0.897) suggested that the test-retest consistency was good at intervals of 2 to 4 weeks. In point of the theoretic concept and development method, the content validity of CWAI scales was satisfactory. The intra-class correlation coefficient for the concurrent validity was 0.650 (P < 0.01) when WAI scales were taken as the criterion. Factor analysis revealed that when eight common factors were drawn from the 17 items of CWAI scales, the cumulative variance of eigenvalues amounted to 71.894%. Each item had communality over 0.60 and its factor loading (0.538 approximately 0.948) attached to the relevant common factor was over 0.40. The common factors with higher factor loading were basically consistent with the theoretic concept of CWAI scales.
  
  
  CONCLUSIONS
  CWAI scales are reliable and valid.
authors.affiliation: Hangzhou Center for Disease Control and Prevention, Hangzhou 310006, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Zhi-Ming
authors.initials: ZM
authors.lastname: Wang
authors.forename: Mian-Zhen
authors.initials: MZ
authors.lastname: Wang
mesh_terms: D006801:Humans; D011361:Professional Competence; D011594:Psychometrics; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires