Why do so many believe that selecting representative study populations is a fundamental research aim for scientific studies? This view is widely held: representativeness is exalted along with motherhood, apple pie and statistical significance. For some researchers this goal can be so important that they would deem a study not worth undertaking if representativeness cannot be achieved. That was the case for two advisors to the U.S. National Children’s Health Study, who resigned when the study design was changed so that representativeness was threatened.2 We admire people who take a stand for principle over expediency, but what exactly is the principle that representativeness embodies? Here we suggest that representativeness may be essential for conducting opinion polls, or for public-health applications, but it is not a reasonable aim for a scientific study.
