It is in the sociological interview—a peculiar form of interaction between observers and subjects—that the act of measurement comes to life. An interview is "a face to face verbal interchange in which one person, the interviewer, attempts to elicit information or expressions of opinions or belief from another person or persons". Interviews may be classified by their degree of structuring, or standardization. Conveying meaning in the schedule standardized interview (SSI) is difficult to achieve, because respondents are from different backgrounds and settings and frequently a phrase or question does not elicit common meaning. With the unstructured schedule interview (USI), questions can be rephrased and reordered to convey meaning, and in the unstructured interview (UI), of course this is even more the case. Whether the interview rests on complex interconnected sets of questions in the form of scales, or relies on open-ended, unstructured questions, the investigator is obligated to report the reliability and validity of his items.