What can you ask about? The effect on response to a postal screen of asking about two potentially sensitive questions

The purpose was to determine whether asking about ethnic origin and housing tenure in a postal survey affects the response rate.

The study derived from a postal survey designed to determine eligibility for a study of outpatients. A two way factorial design was used to look at the two experimental factors, questionnaires being randomly divided into four groups with or without questions about ethnic origin and housing tenure.

10,000 people (1000 from each of 10 areas) were systematically sampled from electoral registers, the areas being chosen to give a nationally representative sample.

The response rate was 66% irrespective of whether ethnic origin was asked about, but was 65% and 67% respectively to questionnaires with and without questions about housing tenure.

Asking about ethnic origin did not affect the overall response to this survey although it is possible that the response from some ethnic minority groups was lower. Asking about housing tenure slightly, but significantly, decreased response.