Psychological testing is a field characterized by the use of small samples of behavior in order to infer larger generalizations about a given individual. The technical term for psychological testing is psychometrics. By samples of behavior, we mean observations of the individual over a limited amount of time performing tasks which have usually been prescribed beforehand, often with a great deal of research into the responses of members of a norm group . These responses are often compiled into statistical tables that allow the evaluator to compare the behavior of the individual being tested to the responses of the range of responses given by people in the norm group. When multiple tests are administered, the procedure is referred to as full battery assessment.

A useful psychological measure must be both valid (actually tests what is claims to test) and reliable (does it consistently).

Types of Psychological Evaluations

Norm-Referenced

IQ/Achievement Tests

IQ tests and academic achievement tests are the most familiar norm-referenced tests for most people. In either of these types of tests, a series of tasks are presented to the person being evaluated, and the person's responses are graded according to carefully prescribed guidelines. After the test is completed, the results can be compiled and compared to the responses of a norm group usually composed of people at the same age or grade level as the person being evaluated.

IQ tests (e.g., WAIS-III, WISC-IV, K-BIT) and academic achievement tests (e.g., WIAT, WRAT) are designed to be administered to either an individual (by a trained evaluator) or to a group of people (paper and pencil tests). The individually-administered tests tend to be more comprehensive, more reliable, more valid and generally to have better psychometric characteristics than group-administered tests. Of course, individually-administered tests are more expensive to administer because of the need for a trained administrator (psychologist, school psychologist, or psychometrician ), and the limitation of working with just one person.

Neuropsychological tests

Neuropsychological tests are specifically designed tasks used to measure a psychological function known to be linked to a particular brain structure or pathway.

They are typically used to assess impairment after an injury or illness known to affect neurocognitive functioning, or when used in research, to measure differences in certain neuropsychological abilities between experimental groups.

Personality tests

Psychological measures of personality are often described as either objective tests or projective tests. Objective tests have a restricted response format, such as allowing for true or false answers. Prominent examples of objective personality tests would be the Minnesota Multiphasic Personality Inventory, Millon Clinical Multiaxial Inventory-III, Child Behavior Checklist or the Abika Test. Projective tests allow for a much freer type of response. An example of this would be the Rorschach test, in which a person states what they see in ten ink blots. The terms "objective test" and "projective test" have recently come under criticism in the Journal of Personality Assessment. The more descriptive "rating scale or self-report measures" and "free response measures" are generally preferred over the terms "objective tests" and "projective tests," respectively. There remains some controversy regarding the value and validity of projective testing. However, those who dismiss these tests seem to ignore the many studies that have supported the sound reliability and validity of scoring systems for the Rorschach (i.e., John Exner's Comprehensive System, Jeffrey Urist's Mutuality of Autonomy Scale) and Thematic Apperception Test (Drew Westen's Social Cognition and Object Relations Scales and Phebe Cramer's Defense Mechanisms Manual). Both self report and free response measures are used in contemporary psychological assessment practice.