The Two Controls
Everyone knows about control groups. They're the people who meet our targeting criteria, but whom we don't treat so that we can understand the incremental impact of our actions. I call these treatment controls, because they allow us to assess the effectiveness of our treatments.
Less commonly, a second kind of control group is used as well, a group call targeting controls. These are people who do not meet our criteria, but whom we treat anyway to check the effectiveness of our targeting.
The truly scientific marketer needs both.