Suppose you are shown the Keen Test of Intellectual Skills, which involves summing the following three physical measurements: (1) the circumference of the subjects head, (2) the length of the subjects nose from tip to eyebrow, and (3) the distance separating the centers of the subjects eyes. You probably realize this test will have very high reliability but is unlikely to be valid. This example is purposely absurd, but the principle it illustrates is important: It is possible for a number of people to take specified measurements from one subject and obtain the same results (measurements), thus showing the tests reliability. However, such measurements may be completely inappropriate for the purposes stated and thus have no validity. Test developers constantly guard against the possibility that their tests may be unreliable or invalid.