Anything can be evaluated if the study is done properly. Social science comes in two forms, which work together.
Qualitative research is about listening to what people say, getting an idea of their feelings, etc.
The idea is that you have to be sensitive to what concerns people. Then you design your evaluative research so that you take this into account. For example, the case study is qualitative, you listen to feelings, etc. In quantitative research design one needs to include a baseline measure before you start treatment for a while. Quantitative research allows you to see change and know it's what you're doing that has had the effect.