One easy way to remember how to evaluate is the acronym MERIT (Method, Ethics, Real world application, Individual Differences, Theory). We could try approaching Zimbardo's prison study from these perspectives. Do you think his study was designed well? Was it ethically sound? Does his study offer any real-world applications or unique insight into human behaviour? Would any potential individual differences affect the generalisability of his study? You can approach any psychology study or theory with this acronym, and it will help you think more critically and broaden your perspectives.