Based on what I know, a moderation analysis is simply looking at an interaction between an IV and a moderator. However, people often refer to moderators when they talk about ANCOVA (analysis of covariance). In this situation though, one of the assumptions of ANCOVA is that there is no interaction between the IV and the covariate.
Why use the term moderator in reference to ANCOVA? And how does one decide if something is a covariate or a moderator? For example, if I am looking at whether a diversity intervention impacts bias scores and I am interested in whether trait empathy moderates (or strengthens) the effect of the intervention, do I look at the interaction between empathy and the intervention, or do I simply add empathy as a "control" or "nuisance" variable in my model?
Apologies if this is a very basic question but there seem to be multiple definitions of the above terms all over the internet, so I would appreciate some clarity. Thanks!