This description from how the US Bureau of Labor Statistics train their interviewers highlights how skilful and expensive it is to conduct high quality in person interviewing: Because of the crucial role interviewers have in the CPS, a great amount of time and effort is spent maintaining the quality of their work. Interviewers are given intensive training, including classroom lectures, discussion, practice, observation, home-study materials, and on-the-job training. Interviewers receive self-study training each month, as well as periodic refresher training sessions. They also are periodically accompanied by a supervisor during a full day of interviewing to determine how well they carry out their assignments.