Item Response Theory-Based Psychometric Investigation of SWLS for University Students

Abstract

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 and adapted to diverse populations, including university students. On the other hand, all these studies were conducted using the classical testing approach, while item response theory was rarely preferred. Regarding this gap, this study aimed to evaluate the psychometric properties of the Turkish version of SWLS by using a graded response model (GRM), which is a member of a broader family of the 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 scale's reliability was acceptable across a wide range of ability spectrums and 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 the IRT context.