Cronbach’s alpha – what makes it really good? Some advice for planning and criticizing psychological questionnaires
Cronbach’s alpha – what makes it really good? Some advice for planning and criticizing psychological questionnaires

Summary/Abstract: Whatever Cronbach’s alpha measures – it’s not internal consistency, commonly misun-derstood in psychology as the average strength of relationships within questionnaireitems. In this article, we explore the reasons why the understanding of alpha as internalconsistency is particularly flawed, and focus on how alpha inflation works in a practicalway. Using the simulation method, we determine the precise (common) influence of thenumber of respondents, the range of measurement (Likert) scales, the number of ques-tions in the questionnaire and the average correlation of items on the alpha level. Theresults confirm alpha-level inflation due to a greater number of questions: alpha getsa satisfactory level even with minimal internal consistency if there are many questionsin the questionnaire. We suggest that the reliability of weak psychological tools is overes-timated because of presented rapid alpha inflation. Number of subjects and the rangeof the scale had no influence on alpha.

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