title: Scale quality: alpha is an inadequate estimate and factor-analytic evidence is needed first of all.
abstract: Cronbach's alpha is a commonly reported estimate to assess scale quality in health psychology and related disciplines. In this paper, we argue that alpha is an inadequate estimate for both validity and reliability - two key elements of scale quality. Omega is a readily available alternative that can be used for both interval and ordinal data. More importantly, we argue that factor-analytic evidence should be presented before assessing the internal structure of a scale. Finally, pointers for readers and reviewers of manuscripts on making judgements about scale quality are provided and illustrated by examples from the field of health psychology.
authors.affiliation: a Department of Health Promotion , Maastricht University/CAPHRI , Maastricht , The Netherlands.
authors.forename: Rik
authors.identifier: 0000-0002-3731-6610
authors.initials: R
authors.lastname: Crutzen
authors.affiliation: b Faculty of Psychology and Education Science , Open University of the Netherlands , Heerlen , The Netherlands.|c Department of Work & Social Psychology, Faculty of Psychology and Neuroscience , Maastricht University , Maastricht , The Netherlands.
authors.forename: Gjalt-Jorn Ygram
authors.identifier: 0000-0002-0336-9589
authors.initials: GY
authors.lastname: Peters
mesh_terms: D001524:Behavioral Medicine; D003627:Data Interpretation, Statistical; D006801:Humans; D007600:Judgment; D011584:Psychology / Q000379:methods* / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires
keywords: Scale quality; alpha; internal consistency; reliability; validity