Evidence-based evaluation

Aims to find measurable changes that can be directly attributed to specific policies. It uses experimental or quasi-experimental research methods. It is evaluation by testing, just as the effect of a medical treatment is assessed in laboratories by administering it to some members of a test group and not to others. By using a large sample group, one can determine the effects of a program or project objectively.  (From The Broker’s Three Approaches to Evaluation: Evaluation Evolution?)