Reliability and validity: Part II.
Determining measurement reliability and validity involves complex processes. There is usually room for argument about most instruments. It is important that the researcher clearly describes the processes upon which she made the decision to use a particular instrument, and presents the evidence available showing that the instrument is reliable and valid for the current purposes. In some cases, the researcher may need to conduct pilot studies to obtain evidence upon which to decide whether the instrument is valid for a new population or a different setting. In all cases, the researcher must present a clear and complete explanation for the choices, she has made regarding reliability and validity. The consumer must then judge the degree to which the researcher has provided adequate and theoretically sound rationale. Although I have tried to touch on most of the important concepts related to measurement reliability and validity, it is beyond the scope of this column to be exhaustive. There are textbooks devoted entirely to specific measurement issues if readers require more in-depth knowledge.