Psychometric Properties of the Kessler psychological distress scale (K6) based on classical test theory and Item-response theory

The purpose of the present study was to investigate the factor structure, convergent and criterion validity gender invariance of Kessler Psychological distress Scale (K6).

In a descriptive-correlation and validation study, 398 people (208 female, 190 male) from Bojnourd residents aged between 18 and 30 were selected by multistage random sampling method and completed Kessler Psychological Distress scale (K6) and Depression, Anxiety and Stress Scale (DASS-21). Exploratory factor analysis, confirmatory and intergroup factor analysis, Pearson`s correlation coefficient, Independent T-Test, discrimination and threshold parameters and item and test information curves were analyzed using SPSS.16 , Amos.20 and IRTPRO 2.1.2 software.

The results showed that the structure of an agent that explains 58.18% of the variance. Confirmatory factor analysis also confirmed this structure. The factor structure of the scale was invariant by gender. The internal consistency of the scale was confirmed by Cronbach's alpha of 0.86 and split-half, 0.83. Convergent validity in relation to depression, anxiety and stress and criterion validity based on gender and age was at a desirable level. The Item-Response parameters were also at the optimum level.

Kessler's psychological stress (K6) seems to have a good validity and reliability in the sample of women and men 18 to 30 years old and can be used as a precise instrument in this regard.