Omega McDonald's is a reliability coefficient similar to Cronbach's alpha. However, the main advantage of omega over Cronbach's alpha is that omega also takes into account the power of connection between items.

https://graphpad.ir/mcdonalds-omega-reliability-coefficient/

Thanks Abolfazl! Also for writing the SPSS macro! Unfortunately, from your answer I can't tell whether you consider Omega suitable for skewed items. Would you say its adequate?

Dear David Schön

Omega coefficient can give reliability under tau- equivalence. Omega corrects the underestimation bias of alfa when the assumption of tau-equivalence is violated (Dunn et al., 2014) and different studies show that it is one of the best alternatives for estimating reliability (Zinbarg et al., 2005, 2006; Revelle and Zinbarg, 2009), although to date its functioning in conditions of skewness is unknown.

But my subjective interpretation is that I don't think there is a reliability coefficient that produces more accurate findings than the omega coefficient in skewed distributions.

For more information:

Trizano-Hermosilla I and Alvarado JM (2016) Best Alternatives to Cronbach's Alpha Reliability in Realistic Conditions: Congeneric and Asymmetrical Measurements. Front. Psychol. 7:769. doi: 10.3389/fpsyg.2016.00769

Deng, L., & Chan, W. (2017). Testing the difference between reliability coefficients alpha and omega. Educational and psychological measurement, 77(2), 185-203.

Hope it helps

Thank you, Hakan Koğar , for your detailed answer! I'll read into the articles you recommended, and go with reporting both alpha and omega. Thanks again and best of health!

David