Personality Tests

Conceptual Overview and Discussion

Personality tests provide an objective anchor for mental health evaluations or research that focuses [Page 672]on mental health issues. Conceptually, personality tests are based on the psychometric method. In brief, the psychometric method seeks to measure psychological variables and then relates these measurements to other psychological variables or observable behaviors. For example, depression can be measured and then examined for its relationship to other mental illnesses or to an observable behavior such as social withdrawal. With these results in hand, clinicians and researchers can better understand the illness of depression and how it achieves behavioral expression. Similarly, aggressiveness can be measured with a standardized test and the results can be compared with a population average to empirically determine whether the individual being assessed is more or less aggressive than the “average” person.

Within the context of formal personality testing the population average referred to earlier is inferred from the normative sample that underpins a test. The normative sample is a group of individuals who are selected to statistically reflect a desired population. For example, the normative sample of a test can be assembled so that the final group reflects the entire U.S. population along important demographic variables such as age, sex, and education. A normative sample of this sort would provide information about how similar or different the person being tested is from the average person. Normative samples can also be assembled to reflect more specific populations. Normative samples, therefore, provide a reference for comparison of individual test scores. The characteristics of the normative sample will determine how a test can be used. Thus, for example, a test that is normed entirely on a criminal population cannot be used to assess a noncriminal patient in a hospital setting.

A personality test—indeed, any test—must first and foremost be valid and reliable. A valid and reliable test measures what it is supposed to measure in a consistent manner. A test of depression, for instance, must actually measure the extent of a patient's depression, and the measurement should not fluctuate randomly each time the patient is tested. As a simpler example, consider the case of a 12-inch ruler as a test of length. Regardless of the number of times an object is measured with this ruler, the result will not vary. This ruler is, therefore, a valid and reliable measurement of length, because it provides consistent information about the length of an object.

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