Interviewers are rarely used, eliminating the cost of hiring, the need for supervision, and potential biasing influence. Nor is there any limitation on delicate subject matter, often present with an interviewer. Since replies are automatically entered into the system as the person responds, there is no need for the expensive process of individual coding of each answer, and the chance for error is lower. Most single-respondent interactive systems provide skip patterns, so that subsidiary questions are always asked when they should be asked and skipped when they should not be asked. Inconsistent responses are noted and brought to the respondent's attention.
Interactive methods have their limitations.
First, only reasonably straightforward questions can be asked. There is no chance for follow-up with probing questions that will define and refine the meaning of answers. Observation Observation is a controlled recording either of events or behavior. It is not a survey method, since it does not involve the usual pattern of questions and answers. Personal observation, using hand counters, has been used for years in clocking pedestrian counts.