Telephone interviews facilitate interviews with respondents across a wide geographic area, and data can be collected relatively quickly. Another advantage of telephone surveys is that they enable interviewers to call back respondents who did not answer the telephone or who found it inconvenient to grant interviews when first called. Using the telephone at a time convenient to the respondent facilitates collection of information from many individuals who would be almost impossible to interview personally. A last advantage is that random digit dialing can be used to select a random sample