Controlled before-and-after study
A more sophisticated type of evaluative research takes into account those unrelated outside forces. A controlled before-and-after study involves two sample groups drawn from the same key public. One sample is the group to receive the message; the other is a control group that does not receive the message.
This process has four elements: 1 observe and measure each group; 2 expose one group to a tactic, but do not expose the control group; 3 measure each group again ; and 4 compare the results of each group