A survey was conducted using a mailed questionnaire which asked about personal habits of the subjects. The subjects were assured that all information would be kept confidential. In addition the respondents were told not to do anything that would reveal their identity in order to maintain the anonymity of their responses. However, each questionnaire had a hidden code placed on it so that the researcher could follow up to reduce the nonresponse rate of the survey and thus increase the reliability of the survey results. What best describes the ethics of this survey