OMEGA is a computational macro for SPSS and SAS that calculates McDonald’s omega for sum scores or averages of multi-item measurement scales. McDonald’s omega is an alternative measure of reliability (compared to Cronbach’s alpha) that has been advocated for by methodologists as it relies on fewer assumptions. OMEGA also calculates Cronbach’s alpha and other statistics.
OMEGA is easy-to-use and available for SPSS and SAS. In addition to calculating omega and alpha, it generates all possible subscales of at least three items from an additive scale containing k items. For each subscale, it generates omega (or alpha) and displays various information about that subscale (such as the subscale-full scale correlation). Summary statistics of individual items and the full scale are also generated. For a full description of OMEGA and its features, read the documentation in the download folder.
In addition to the syntax version for SPSS users, there is a dialog box based on the graphical user interface (GUI). Not all options are available, but the dialog box can be permanently installed and used for simple estimation.