The respondent is contacted after the research and questioned about the interview and the interviewer. This process authenticates the collected data by ensuring responses were provided by the actual respondent.
The subsequent re-contacting of respondents in a survey to check that the proper procedures have been followed, e.g. the respondent was qualified to be included in the survey, the responses recorded were accurate or even that the interview actually took place. Validation can be performed by the data collection company and/or the client, in person, by telephone, or by mail.