Suppose that I want to relate three variables, and a causal link between each two of them is proposed depending on the available literature, and I may too propose that one of these variables is the mediating variable.
So my thesis supervisor told me that to test cause-effect relationships we can use regression.
But I am not sure what is the research design then?
I know studying causal relationships can apply in experimental, quasi-experimental and ex post facto designs, depending on the variables and the conditions. But I don't know what research design allows multiple regression?