one of our first contributions, and one which initially seemed counterintuitive to our client, was to narrow its previously used research sample of all potential new car buyers to only those why would consider an AMC car. Our rationale was that the data from nonconsiderers of AMC had been distorting the research because these responses tended not only to be more negative, but also were more heterogeneous and generated more random error.
The shift to a sample on only AMC considerers was more costly, but was ultimately warmly embraced by the client because it led to more sensitive and accurate research results.