The usefulness of the Basic Question Procedure for determining non-response bias in substantive variables - A test of four telephone questionnaires

The Basic Question Procedure (BQP) is a method for determining non-response bias. The BQP involves asking one basic question - that is, the question relating to the central substantive variable of the study - of those persons who refuse to participate in the survey. We studied the usefulness of this method in four telephone surveys by comparing it with the results obtained in 'refusal conversion' studies. (1) Does the BQP enable us to collect information on the central substantive variable of a study from a larger number of non-respondents than we can collect with the 'refusal conversion' procedure? (2) Do respondents and refusers differ in their answers to the basic question? The answer to both questions is affirmative. Using the BQP, we can interview at least as many, but often more refusers than in refusal conversion studies. Moreover, respondents and refusers differed in their answers to the basic question. In particular, refusers answered more often 'don't know' or 'no opinion'.