New Developments in the Sampling of Special Populations

This paper describes alternative methods for careful sampling of special populations. It discusses the use of single or multiple lists, even when incomplete, along with supplementary measures using telephone and mail techniques. If the special populations are clustered there are several alternatives for reducing costs substantially. These involve telephone or mail screenings to eliminate zero segments with a single contact, use of two or three contacts to eliminate zero segments if face-to-face screening is required, use of lists to identify nonzero segments, use of combined screening, and reducing the sampling rate in nonzero areas that have low densities. For some populations the use of network sampling can be very effective. Some populations can be defined by their activities and sampled at locations where they participate. These careful methods should be used if one is trying to generalize to a total special population.