How to deal with hard to survey populations

Some populations are hard to survey because they are hard to find, others because they are hard to sample and still others because they are hard to persuade to participate in surveys. Some are simply hard to interview. Examples of hard-to-survey populations include migrants, immigrants, homeless people, persons with intellectual difficulties, the visually impaired, drug users, political extremists, sex workers and people in difficult settings such as war zones or homeless shelters.

By Kevin Gray, president of Cannon Gray, a marketing science and analytics consultancy.