|Title||Reflections on and test of the metrological properties of summated rating, Likert, and other scales based on sums of ordinal variables|
|Author(s)||Kampen, Jarl K.|
|Source||Measurement 137 (2019). - ISSN 0263-2241 - p. 428 - 434.|
Mathematical and Statistical Methods - Biometris
|Publication type||Refereed Article in a scientific journal|
|Keyword(s)||CESD - Depression - Likert scale - Measurement level - Metrology - Ordinal - Summated rating scale|
This study aims to contribute to the perpetual controversy on the parametric analysis of ordinal data, by giving a perchance long overdue examination of the widely held notion that sums of ordinal variables (e.g., Likert and summated rating scales) produce measures at ordinal level. In the present study, all 1,048,574 subscales of a well-known and widely applied sumscale, the 20-item CESD scale for depression, were assessed for their metrological properties. It was found that subscales consisting of less than 60% of the items of the original scale have lost all metrological properties of that scale, including ordinality as measured by Kendall's tau. This result justifies concern about the robustness of measurement scale properties of (shortened) sumscales, and by implication, of the empirical findings based on such scales.