An article found here provides a good example of how a test can be valid for one purpose but invalid for another. In this case, the test is the Wonderlic Contemporary Cognitive Ability Test and it has been used for years by the NFL to help teams decide which players to draft from the college ranks. The problem is that cognitive ability is not as predictive of athletic performance as it is of academic performance. As a case in point, quarterback Johnny Manziel achieved a high score on the test and had an undistinguished two-year NFL career whereas repeat SuperBowl champion quarterback Tom Brady scored quite low but played for more than 20 years with two different teams and will be inducted into the NFL Hall of Fame.