Most researchers will choose a study done by the research group, and is trying to prevent the exchange of information between the control group and the experimental group.
Most researchers will study done by one group. For the convenience of the research is to try and prevent the exchange of information between the control group and the experimental group.
Most researchers to select the study done to one group. For the convenience of the researcher and is trying to prevent the exchange of information between the control group and the experimental group.