Using Rasch Measurement to Create a Quality of Sleep Scale for a Non-Clinical Sample Based on the Pittsburgh Sleep Quality Index (PSQI)

Originally, the aim of the present study was to investigate the psychometric properties and the appropriateness of the Greek version of the PSQI for a non-clinical sample. However, the scale was deemed not to be appropriate and results suggested some major modifications (study 1). The modified scale was administered to a second sample of Cypriots and was shown to be unidimensional and to have a high degree of reliability (study 2). The items define a theoretical linear quality of sleep continuum of increasing difficulty and cover a wide range of that continuum. Furthermore, a 3-point (instead of the original 4-point) Likert scale was shown to be optimal and the scale was found to be appropriate for a non-clinical sample. The resulting scale is suitable for research purposes in studies regarding quality of sleep in academia, medicine and marketing. It could be used either for individuals or for large scale samples.