I try to run a Mediation analyses. Unfortunately PROCESS by Hayes doesn't allow dichotomous variables.
How can I solve the Problem? How can I calculate for direct and indirect effects?
My variables are:
x: Softness (categorial: soft, middle, hard)
y:sample size, metric
Mediator: study design (dichotomous: experiment vs. quasi-experiment)
Softness of the discipline is the predictor (Smith et al. 2000 found out that some (psychological) disciplines are rated as softer than others e.g. educational Psychology is "softer" than Neuroscience). This should directly effect the sample Size (Marszalek et al.2011 found out that different subdisciplines varies in size of sample collection per study). Marszalek 2011 guess this direct effect could be mediated by study design, as "harder disciplines" run more experiments than softer disciplines (they probably Use more quasi-experimental designs) and the study design should effect the sample size e.g. experiments need a smaller sample to detect an effect, because standard error is usually smaller than in quasi experimental designs and confounders are smaller or easier to controll compared to quasi-experimental Designs.