What is the distinction between a relationship and a difference in the context of statistics - if you have a nominal variable and an interval variable, when should you use a correlation to measure the relationship, rather than a t-test or an ANOVA?
I'm not after the usual 'what is your question about - relationships or differences' (although I obviously appreciate the importance), but rather what is it about the data or the constructs that I should know to make this decision.
If for example you have males and females and their intelligence scores. Is there a statistical/conceptual reason why a t-test is better here than a point-biserial correlation?
This is probably going to be an obvious question. To be honest though, I don't feel like I've ever really understood the distinction, so perhaps some of you can articulate it for me?