PSYCHOLOGICAL CONSULTATION
Psychological consultation in its most basic form is a problem solving process. It differs from psychotherapy because it is not a one-on-one process with a single client. The problem usually involves a family, a group, a student, an organization or an issue. Psychological consultation involves the process of identifying the problem(s) and applying psychological principals to help solve the problem.

PSYCHOLOGICAL ASSESSMENT
Psychological assessment is one of the skills that a psychologist uses to help with the diagnosis of mental disorders, learning problems, and planning intervention. Psychological testing or psychological assessment is characterized by the use of small samples of behavior in order to infer generalizations about a given individual. The technical term for the science behind psychological testing is psychometrics. By samples of behavior, one means observations over time of an individual performing tasks that have usually been prescribed beforehand. These samples are gathered in face to face interactions or by using self administered tests via paper/pencil or computer.  Other samples are gather from interviews with persons who know the individual being evaluated or by having those persons complete checklists or surveys about the person being assessed.  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 a norm group. When multiple tests are administered, the procedure is referred to as full battery assessment.

A useful psychological measure is both valid (actually measures what it claims to measure) and reliable (is internally consistent or give consistent results over time).

TYPES OF PSYCHOLOGICAL EVALUATIONS
There are several broad catagories of psychological evaluation tests:

Norm Referenced
Norm-referencing tests regard a specific or non-specific topic, often pertaining to the test taker's education, or career. These tests are commonly used in high schools and colleges. The results often correlate to a Bell curve -- with a few participants doing badly, most doing average, and a few doing extremely well. A common norm-referencing test in the United States is the Graduate Record Examination (GRE), which measures the general area of critical thinking, verbal reasoning and quantitative reasoning skills. In addition, specific GRE subject tests however cover eight broad fields, mainly in the sciences, but also in mathematics and English.

Intelligence/Achievement Testing
Intelligence / cognitive tests and academic achievement tests are the most common norm-referenced tests. In either of these types of tests, a series of tasks is 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 comprised of people at the same age or grade level as the person being evaluated.
IQ tests (e.g., WAIS-III, WISC-IV, K-BIT-2) and academic achievement tests (e.g., WJ-III, MBA) 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. However, individually-administered tests are more expensive to administer because of the need for a trained administrator (psychologist, school psychologist, or psychometrician) and because of the limitation of working with just one client at a time.

Neuropsychological Tests
These tests consist of 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 contast neuropsychological abilities across experimental groups.

Personality Tests
Psychological measures of personality are often described as either objective tests or projective tests.

Objective Tests
Objective tests have a restricted response format, such as allowing for true or false answers. Prominent examples of objective personality tests include the Minnesota Multiphasic Personality Inventory, Personality Assessment Inventory, Millon Multiaxial Multiaxial Inventory-III, Behavioral Assessment System for Children, Child Behavior Checklist, and the Beck Depression Inventory.

Projective Tests
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 each of ten ink blots might be.

Direct Observation Tests
Although most psychological tests involve "rating scale" or "free response" measures, psychological assessment may also involve the observation of people as they complete activities. This type of assessment is usually conducted with families in a laboratory, home or with children in a classroom. The purpose may be clinical, such as to establish a pre-intervention baseline of a child's hyperactive or aggressive classroom behaviors or to observe the nature of a parent-child interaction in order to understand a relational disorder. Direct observation procedures are also used in research, for example to study the relationship between intrapsychic variables and specific target behaviors, or to explore sequences of behavioral interaction.

Psychological Evaluations Using Data Mining
An examiner may use data mining methods to draw inferences from existing records, texts, and datasets about the person. This process involves gathering data on the individual from sources such as public records, behavior history records, consumer activities, shopping histories, memberships in various organizations, court records, demographic data, and information submitted by friends, co-workers, relatives.
This article retrieved and modified from http://en.wikipedia.org/wiki/Psychological_testing