Reliability

Reliability refers to the consistency or stability of a measurement. A test or instrument with good reliability means that the respondent will obtain the same score on repeated testing as long as no other extraneous factors affect the score. In actuality, a respondent will rarely obtain the exact same score over repeated testing because repeated assessments of any phenomenon will likely be affected by chance errors. Thus, the goal of testing is to minimize chance errors and maximize the reliability of the measurement with the recognition that a perfectly reliable measure is rarely attainable. Although a highly reliable test will not yield identical scores for a participant from Time 1 to Time 2, the scores will tend to be similar if the test is reliable. ...