A psychological test is an instrument designed to measure unobserved constructs, also known as latent variables. Psychological tests are typically, but not necessarily, a series of tasks or problems that the respondent has to solve. Psychological tests can strongly resemble questionnaires, which are also designed to measure unobserved constructs, but differ in that psychological tests ask for a respondent’s maximum performance whereas a questionnaire asks for the respondent’s typical performance. A useful psychological test must be both valid (i.e., there is evidence to support the specified interpretation of the test results) and reliable (i.e., internally consistent or give consistent results over time, across raters, etc.).
It is important that people who are equal on the measured construct also have an equal probability of answering the test items correctly. For example, an item on a mathematics test could be “In a soccer match two players get a red card; how many players are left in the end?”; however, this item also requires knowledge of soccer to be answered correctly, not just mathematical ability. Group membership can also influence the chance of correctly answering items (differential item functioning). Often tests are constructed for a specific population, and this should be taken into account when administering tests. If a test is invariant to some group difference (e.g. gender) in one population (e.g. England) it does not automatically mean that it is also invariant in another population (e.g. Japan).
A comparative account on aptitude test, achievement test and intelligent test can be outline below;
An aptitude test is designed to assess what a person is capable of doing; to predict what a person is able to learn or do given the right education and instruction. It represents a person’s level of competency to perform a certain type of task.
Some examples of aptitude tests include:
• A test assessing an individual’s aptitude to become a fighter pilot
• A career test evaluating a person’s capability to work as an air traffic controller
• A test given to high school students to determine which type of careers they might be good at
Unlike achievement tests, which are concerned with looking a person’s level of skill or knowledge at any given time, aptitude tests are instead focused on determining how capable of a person might be of performing a certain task.

An achievement test is designed to measure a person’s level of skill, accomplishment, or knowledge in a specific area. Some examples of achievement tests include:
• A math exam covering the latest chapter in your book
• A test in your social psychology class
• A comprehensive final in your Spanish class
• A skills demonstration in your martial arts class
Each of these tests is designed to assess how much you know at a specific point in time about a certain topic.
Achievement tests are not used to determine what you are capable of; they are designed to evaluate what you know and your level of skill at the given moment.
Achievement tests differ in important ways from aptitude tests. An aptitude test is designed your potential for success in a certain area. For example, a student might take an aptitude test to help determine which types of career they might be best suited for. An achievement test, on the other hand, would be designed to determine what a student already knows about a specific subject.
It could also be a test, typically standardized, which is designed to measure subject and grade-level specific knowledge. Achievement tests are frequently used as a way to determine at what level a student is performing in subjects such as math and reading.
Intelligence tests are psychological tests that are designed to measure a variety of mental functions, such as reasoning, comprehension, and judgment. The goal of intelligence tests is to obtain an idea of the person’s intellectual potential. The tests center around a set of stimuli designed to yield a score based on the test maker’s model of what makes up intelligence. Intelligence tests are often given as a part of a battery of tests.

There are many different types of intelligence tests and they all do not measure the same abilities. Although the tests often have aspects that are related with each other, one should not expect that scores from one intelligence test, that measures a single factor, will be similar to scores on another intelligence test, that measures a variety of factors. Also, when determining whether or not to use an intelligence test, a person should make sure that the test has been adequately developed and has solid research to show its reliability and validity. Additionally, psychometric testing requires a clinically trained examiner. Therefore, the test should only be administered and interpreted by a trained professional.
A central criticism of intelligence tests is that psychologists and educators use these tests to distribute the limited resources of our society. These test results are used to provide rewards such as special classes for gifted students, admission to college, and employment. Those who do not qualify for these resources based on intelligence test scores may feel angry and as if the tests are denying them opportunities for success. Unfortunately, intelligence test scores have not only become associated with a person’s ability to perform certain tasks, but with self-worth.
The four most commonly used intelligence tests are:
• Stanford-Binet Intelligence Scales
• Wechsler-Adult Intelligence Scale
• Wechsler Intelligence Scale for Children
• Wechsler Primary & Preschool Scale of Intelligence

A criterion-referenced interpretation of a test score compares an individual’s performance to some criterion other than performance of other individuals. For example, the generic school test typically provides a score in reference to a subject domain; a student might score 80% on a geography test. Criterion-referenced score interpretations are generally more applicable to achievement tests rather than psychological tests.
Often, test scores can be interpreted in both ways; answering 80% of the questions correctly on a geography test could place a student at the 84th percentile (that is, the student performed better than 83% of the class and worse than 16% of the classmates), or a standard score of 1.0 or even 2.0.

• Anastasi, A., & Urbina, S. (1997). Psychological testing (7th ed.). Upper Saddle River, NJ: Prentice Hall.
• • Mellenbergh, G.J. (2008). Chapter 10: Surveys. In H.J. Adèr & G.J. Mellenbergh (Eds.) (with contributions by D.J. Hand), Advising on Research Methods: A consultant’s companion (pp. 183-209). Huizen, The Netherlands: Johannes van Kessel Publishing.
• • American Educational Research Association, American Psychological Association, & National Council on Measurement in Education. (1999). Standards for educational and psychological testing. Washington, DC: American Educational Research Association.
• • Mellenbergh, G.J. (1989). Item bias and item response theory. International Journal of Educational Research, 13(2), 127–143.
• • Standards for Education and Training in Psychological Assessment: Position of the Society for Personality Assessment – An Official Statement of the Board of Trustees of the Society for Personality Assessment. Journal of Personality Assessment, 87, 355–357.
• • Robert J. Gregory (2003). “The History of Psychological Testing”. Psychological Testing : History, Principles, and Applications (PDF). Allyn & Bacon. p. 4 in chapter 1. ISBN 9780205354726.
• Jiannong Shi (2 February 2004). Robert J. Sternberg, ed. International Handbook of Intelligence. Cambridge University Press. pp. 330–331. ISBN 978-0-521-00402-2.


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