Final answer:
Option D. The advantage of interview surveys over mail surveys that is NOT correct is (D) the anonymity of respondents. Interview surveys typically have higher response rates and allow for immediate clarification but do not offer better anonymity than mail surveys.
Step-by-step explanation:
Out of the options provided regarding the advantages of interview surveys over mail surveys, anonymity of respondents (D) is NOT one of those advantages. Interview surveys tend to have higher response rates (A) because the interviewer can encourage participation and ensure the survey is completed. They also allow for immediate clarification of questions (B) as the respondent can ask for explanations or the interviewer can ensure understanding before the respondent answers.
However, interview surveys are generally not as cost-effective (C) as mail surveys due to the need for trained interviewers and potentially travel expenses. In contrast, mail surveys can provide greater anonymity, which is essential when asking about sensitive or personal issues, leading to more honest responses.