Reliability and validity of psychological tests vary with how they are used.
Psychological tests have the highest reliability and validity when administered and interpreted by a qualified mental health professional. Though psychological tests are useful, no test or combination of tests can completely assess a person, because human psychology is too complex.
Reliability refers to whether a test is consistent, over time, in its results. A good test must also be internally consistent. Validity refers to whether test results describe a person’s actual behavior. For most psychological tests, reliability is higher than validity, which underscores the need for additional information, such as interviews.
Reliability and validity are crucial to quality psychological testing. If reliability isn’t present, then the test can’t be trusted to make valid assessments in a clinical setting. If validity isn’t present, then the test can’t be trusted to make predictions about behavior in a real-world setting.
The Minnesota Multiphasic Personality Inventory (MMPI), a staple in clinical settings, is also being used increasingly for occupational screening. Its validity in screening job applicants is problematic because it wasn’t designed to make broad predictions such as who will do well in a specific career.
One of the most popular personality tests, the Myers-Briggs is a test whose reliability and validity are controversial. The National Research Council reported that the Myers-Briggs’ reliability ranged from 24 percent to 61 percent and that its validity, while adequate for measuring where a person falls on its introversion to extroversion spectrum, is weak for measuring its other spectra of traits.