get_reliability(): Display all alphas when different index variables are dropped

[LKobilke]

Currently, the get_reliability() function computes reliability estimates of index variables created with add_index. However, we could think about an option that shows all alpha values when different index variables are omitted.

A possible way to implement this feature could be through an additional argument that triggers an additional output of alpha values for each scenario where a different index variable is dropped (similar to post hoc option in unianova() ). Otherwise, we could think about providing an additional function, such as check_reliability.

[MarHai]

That would be a great addition and I think we should not introduce another verb but instead use a parameter within get_reliability.