Most potential respondents are more likely to complete a lengthy mail survey at their convenience than take 15-20 minutes for a telephone survey. Data Quality Interviewer Effects on Responses Careful training is required for any quality telephone survey program. Even then, an interviewer's presence can influence survey results by mood or tone. Respondents may also feel pressure to give socially desirable responses. Mail survey respondents are less likely to feel this pressure, and have the advantage of being able to re-read questions and think about appropriate responses.
Respondents are more likely to divulge personal information in a mail survey.
Anonymity and Confidentiality A majority of respondents indicate that mailed surveys are not intrusive. In contrast, telemarketing conducted in the guise of conducting surveys has resulted in the public sentiment that telephone surveys are intrusive. As a result, legislation has been introduced in over 25 states, specifically directed at limiting unsolicited telephone calls. Although the proposed legislation is aimed primarily at curbing unwanted telemarketing calls, these laws would make it harder and more expensive to do telephone surveys. When respondents' names are used, perceived confidentiality can be affected in both mail and telephone surveys.