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Term Definition
Official statistics

Statistics complied by or on behalf of government departments or agencies.

Ontology, ontological

A theory of the nature of social entities.

Open question, open-ended question

A question used in an interview or questionnaire where the respondent does not have to choose from a list of pre-defined responses. The respondent is allowed to reply to the question in his or her own words.

Oral history interview

A largely unstructured interview in which the respondent is asked to recall events from his or her past and to reflect on them.

Ordinal variable

A variable whose categories can be rank ordered from highest to lowest (as in the case of interval and ratio variables), but the distances between the categories are not equal.


An extreme value in a distribution of values. It will either be much higher or much lower than other values in the distribution. The presence of outliers can distort the mean.