The sampling frame is a list of population units that can be sampled. Examples
include electoral register, phone directory, area maps for door-to-door sampling, retail census for outlets and lists supplied by clients
such as for customer satisfaction studies.
Sampling frames normally do not correspond exactly with target population. Coverage gaps exist, for instance,
homes without telephones, inaccessible homes (door-to-door survey) or inaccessible outlets (retail tracking).
