If it's generic, it's unclear which study you're evaluating. So if you get asked to evaluate Genie (unit 3 example) and you say it was a case study involving a unique individual situation, therefore the results can't be generalised, you wouldn't get the mark because it's generic, you could be talking about any case study. If you specified it was a case study, in which Curtiss used observations and neurological tests to see..., then it's specific.
But just because your evaluation point is specific, that doesn't mean it will get a mark. For example, you could say: A weakness of Curtiss' case study of Genie is that it was highly suspected that she suffered from mental retardation, so the study lacks validity. It's clear that you're talking about Genie and nobody else, but it's not developed. You could develop it by saying: ...so the conclusions drawn about a sensitive/critical period for language development may not be valid, as it could be that the cause of her inability to develop language is the mental retardation, and not the effects of privation.
(This is just be trying to reassure myself that I won't fail)