As a working definition, privacy can be understood as seclusion and protection from others and more specifically the right to limit access to some aspect of their persons. There are also specific types of personal information, for example, recent legislation in the UK makes specific provision for sensitive personal data which includes: racial or ethnic origin, political opinions, religious or other beliefs, trade union membership, health, sex life and criminal proceedings or convictions (UK Data Protection Act 1998). In relation to survey data, personal information can be thought of as information relating to an identified or identifiable individual. It could include opinions about the individual.
Confidentiality can be understood as a contractual form of privacy i.e. a promise made by a data collector to a data provider and usually relates to issues of anonymisation and data use. The 2001 UK Census included the following confidentiality commitment:
"The Information you provide is protected in law and treated in strict confidence. The information is only used for statistical purposes and anyone found disclosing census information improperly will be liable to prosecution. Census forms will be held securely. Under the current terms of the Pubic Records Act 1958, the data will be treated as confidential for a period of 100 years".
The Office of National Statistics has added to this that individuals should not be able to identify themselves in the data. For a list of the different assurances given on UK census forms dating back to 1851 see Hakim, C. (1979) "Census Confidentiality in Britain" in Bulmer, M. (ed.) Censuses, Surveys and Privacy, London, Macmillan