Item Response Theory based Psychometric Investigation of SWLS for University Students
Keywords:item response theory, satisfaction with life, differential item functioning
Life satisfaction is an important factor for mental health and has many positive effects on people. Considering its importance, different measurement tools were developed over the last 5 years. Among these tools, the Satisfaction with Life Scale (SWLS) is the most prominent one and adapted to diverse populations including university students. On the other hand, all these studies were conducted with classical testing approach while item response theory was rarely preferred. Regarding this gap, the aim of this study was set as evaluating the psychometric properties of Turkish the version of SWLS by using a graded response model (GRM), which is a member of broader family of modern psychometric approach called Item Response Theory (IRT). For this purpose, the data were collected from 471 university students (male = 83, female = 388) aged between 17 and 37 years (M = 21.23, SD = 2.32). IRT based analysis provided satisfactory results on the psychometric properties of the SWLS. It was found that the reliability of the scale was acceptable across a wide range of ability spectrum, items fit the GRM well and did not show gender-based differential item functioning. As a result, the psychometric quality of SWLS was further proved in IRT context.