Questionnaires pose a structured and standardized set of questions, either to one person, to a small population, or to respondents in a sample survey. Structure refers to questions appearing in a consistent, predetermined sequence and form. A questionnaire might, for example, commence with experiences from the subject's childhood, proceeding through time to the present. Questionnaire items follow characteristic forms: open-ended questions, where respondents fill in the blank, using an original choice of words; or the closed response format, where responses must conform to options supplied by the interlocutor. Seemingly minor alterations in wording can substantially affect responses, a phenomenon which has generated much methodological research. A questionnaire administered in a face-to-face interview, or over the telephone, is generally termed a 'schedule'. In deciding upon one of these methods, researchers balance off costs, probable response rate, and the nature of the questions to be posed.