A test’s reliability is the extent to which test scores are consistent over repeated sittings. This concept is critically important in standardized testing, and reliability is a key reason why test scores have meaning. Candidates with the same ability should always get close to the same score. If there is a great deal of inconsistency in the scores, then the test cannot provide a consistent assessment of what it is supposed to measure.
This article discusses five issues that can reduce test reliability and what we do on the GMAT exam to minimize these threats.