Question about using cronbach alpha

I've applied a questionnaire about COVID-19 and social isolation to 415 people. I have 15 questions that range from 0 (no stress at all) to 3 (high level of stress) with topics like "family conflicts".
I studied the 15 parameters individually and how they related to the subject's anxiety.
My question is: can I use the Cronbach alpha to investigate consistency given that I'm using them individually? Is there a better method to get this information? Can I use the individual alpha (from Cronbach) for each of the 15 parameters?

Thanks in advance.


So Cronbach Alpha is a measure of internal consistency and it is typically used as a way to assess reliability. Cronbach is performed by adding a set of independent variables together (you can do it for a set of questions that constitute your dependent variable too) and then to calculate alpha which indicate greater agreement or lesser agreement.

You cannot look at Cronbach's alpha for 1 item. Hence all the items you include should be related to the same construct. Thus, if you have 15 items that specifically relate to anxiety then you can perform Cronbach's alpha once with all 15 items included. If you have smaller constructs within anxiety, you should group those and perform the analysis for specific sets. All of these considerations should be be based on the theoretical reasons you chose that specific set of questions/scale/inventory.

SPSS and I am sure R will have smiliar routines where you can add all the item and then you can also see which item lowered the overall reliability and in that way find an optimal set to enhance the internal consistency but once again caution should be applied in how this is performed and how item exclusion is done (i.e. did participants fail to read the question properly etc etc etc).

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Thank you so much!
Just a question, should I report the alpha in general or all the alpha values for each parameter?

I'd suggest that you need to talk to a good psychometrician. I am not as up-to-date on my pschometrics as I should be but as @
says you can not validly report a Cronbach Alpha on a single question. It does not make any sense. If you are reporting on individual variables, I do not see how you can report an overall alpha because it would only be valid in the context of treating all 15 items as a unit.

I think you are misunderstanding the concept of a Cronbach Alpha but I imagine we would have to know more about the premises of the study to suggest anything else.

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In general, there is a new tool as well:

both can be calculated in Jamovi:

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