The Cronbach-Mesbah Curve for assessing the unidimensionality oh an item set: the R package MCM

This paper describes the R package CMC that calculates and plots the step-by-step Cronbach Mesbah curve. This is a simple but effective method, based on the Cronbach coefficient of reliability that can be used for checking the unidimensionality of a measurement scale adopted in a psychological or social science survey. So far this graphical tool has been implemented only in an SAS macro called ANAQOL and therefore its dissemination has been somewhat limited to SAS users. The main aim of the CMC package is to extend the use of this method to a wider scientific community. To pursue this goal, the package is written in the open-source R language, which is rapidly evolving as the lingua franca of data analysis and statistical computing in many scientific fields. This paper illustrates the Cronbach-Mesbah curve via simulated datasets from the Rasch model.