Reliability is defined as the extent to which a questionnaire, Test, observation or any measurement procedure produces the same results on repeated trials. In short, it is the stability or consistency of scores over time or across raters. Keep in mind that reliability pertains to scores not people. Thus, in research we would never say that someone was reliable. As an example, consider judges in a platform diving competition. The extent to which they agree on the scores for each contestant is an indication of reliability. Similarly, the degree to which an individual s responses (i.e., their scores) on a survey would stay the same over time is also a sign of reliability.