An Item Response Theory Analysis and Psychometric Properties of the Czech Version of the Satisfaction with Life Scale

The original version of the Satisfaction with Life Scale (SWLS) has been successfully tested in many studies, mainly using Classical Test Theory (CTT). Using Item Response Theory (IRT), this study examines psychometric properties of the original SWLS comprising five items, and its abbreviated versions and possible usage of a shorter response scale in a Czech data sample. IRT analysis was used to test the psychometric properties of the original SWLS, compris-ing five items rated on a 7-point Likert scale, and its results were compared the abbreviated version with four (SWLS-4) and three items (SWLS-3) and was also applied to evaluate the adequacy of the response scale's length. For the analysis, data from a representative sample of the Czech population older than 18 years were used (N = 1, 000). The results showed that all the three tested versions of the SWLS reached excellent psychometric properties, includ-ing unidimensionality, with slight differences between them. Further testing of the response scale's adequacy indicates that shortening the response categories from seven to five will be appropriate. The results of this Czech study show that abbreviated versions of the SWLS can be used interchangeably without impacting its psychometric qualities. The results also confirm that a shorter response scale is appropriate for the application. The findings from measurement invariance indicate that the SWLS allows meaningful comparisons in life satisfaction across gender and age.