The information requested falls within the responsibility of the National Statistician, who has been asked to reply.
Letter from Colin Mowl, dated May 2007:
The National Statistician has been asked to reply to your recent Parliamentary Question asking how the Office for National Statistics (ONS) chooses people for interview in the course of compiling its statistics; what obligation there is on such. people to respond; what guidance the ONS gives to such people. I am replying in her absence. (135806)
The ONS interviews people as part of its Social Survey Programme. Addresses are selected at random from the Royal Mail’s Postcode Address list. Residents at those addresses are then interviewed. Participation in the survey is voluntary.
All households selected for interview receive an early warning letter from the Office. This letter explains the purpose of the survey, the selection procedures and encourages participation. It also describes on whose behalf the survey is being conducted. In some cases a small reward (in the form of a gift voucher) is offered on completion. The letter also provides details of the interviewers and offers an inquiry line for questions.
When interviewers call at the address they provide interviewees with a leaflet which covers many of the points referred to above, in more detail. This leaflet also explains to respondents that data obtained in the interview are confidential and are used for statistical purposes only. When asked whether the interviews are mandatory, interviewers are trained to explain that they are conducted on a voluntary basis. I am placing a copy of a sample of the leaflet and introductory letter in the House of Commons Library.
ONS also interviews people at airports for the International Passenger Survey, where people are again selected randomly at the Departures and Arrivals areas of ports and airports. In addition ONS does sometimes interview people via telephone to follow up social survey interviews first conducted face-to-face, as described above.