Definitions for "Random Digit Dialing"
Random digit dialing is when researchers sample from a compilation of all possible telephone numbers, including unlisted ones (17). Some researchers try to measure public opinion by calling every 50th residential number in a telephone book. This survey method excludes cell phone users, unlisted numbers, and people who do not have a telephone.
Rather than selecting names and numbers of individuals to be called, computers are used to generate random sets of seven-digit numbers, which are then called as the survey sample.
Techniques that form samples by adding random digits to the telephone prefixes that fall within the sampling area so as to include listed (published) and unlisted numbers in the sample.