In Person (Face-to-Face) Sampling

National samples for face-to-face surveys are typically drawn by an area probability method, which relies on US Census figures and maps of the country. For example, the 2016 ANES used a multi-stage process to draw its national sample. This process is called a multistage stratified cluster sample, and has a long history of use in face-to-face surveys. The stages were:

1. Selecting primary sampling units (PSUs) from the 48 contiguous states and Washington, DC. (For the face-to-face survey, cost considerations precluded interviewing respondents in Alaska and Hawaii. Respondents in those states were, however, included in the Internet sample.) The PSU's were counties or portions of counties (Los Angeles County was divided into two PSU's because of its large area). The PSU's were then listed by what Census region they were in, the prevalence of poverty in the county, size of minority population, and population size. Sixty PSU's were then chosen from this list; the probability of being chosen was based on the number of adult citizens in the PSU, so larger population PSU's had a higher chance of being selected and smaller ones had a lower chance. Cook County, IL (Chicago area), Harris County, TX (Houston area), Maricopa County, AZ (Phoenix area) and both halves of the Los Angeles County PSU were included in the sample of PSU's.
2. Four secondary sampling units were then identified in each PSU.
3. Within each secondary sampling unit, individual households were randomly chosen using the US Post Office's computerized delivery sequence file (DSF). Each of the selected household received a study brochure and $5 in cash.
4. An eligible person to be interviewed in the each household was then randomly identified by an interviewer who visited the household.

Interviewees received either $25 or $50 as incentives to complete the interview. As the study went on, this was increased to $100 for non-respondents.