Factors affecting reliability in a psychological test

Written by melanie j. martin
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Factors affecting reliability in a psychological test
Many factors influencing a test's reliability relate to the test-taker's ability to concentrate. (taking test image by Petro Feketa from Fotolia.com)

For years, psychologists have known that psychology tests are not always reliable. Even the most effective methods of evaluation are not completely objective because of numerous variables. When giving evaluations, psychologists must work to minimise these factors or take them into consideration when interpreting the results of the test.

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Nutrition and Sleep

The body's physical demands play a large role in how well a test-taker can concentrate. As the authors of "The GRE Test for Dummies" say, nutrition improves mental functioning. Before any test, from the SAT to a psychological evaluation, test-takers must get a full night of sleep and eat a good breakfast. Using good nutrition habits well before the test may help, too.


The setting should provide a quiet, comfortable place for the test-taker to work without interruption. If conversations are taking place within hearing distance, that will probably distract and slow him. Likewise, if the room is very hot or cold, he may have trouble focusing.

Attention Span

A psychological test should match the test-taker's attention span, too. If not, the test-taker will probably become frustrated and the results will become skewed, as Gary Groth-Marnat says in "Handbook of Psychological Assessment." He suggests administering shorter forms of the test if the evaluator (i.e., the psychologist) feels that would be more appropriate.

Reading and Education Level

The test-taker's reading level must also match the level of the written materials in the test, and her education level should match the test as well, as Groth-Marnat points out. Otherwise, the test-taker may not be able to understand the materials or complete the test in the required time frame (if any). She could also become frustrated or lose focus.

Learning Disabilities

Likewise, if the test-taker has learning disabilities, they will affect the speed and accuracy in which he answers questions. The evaluator could administer a modified version of the test, such as an oral test instead of a written one, or administer the test in shortened chunks while waiving the time limit, if appropriate.


The test-taker's motivation also plays a role in the accuracy of the results. For results to be accurate, the test-taker must truly strive to answer them truthfully and seriously, as the website A Guide to Psychology and Its Practice says.


Often an evaluator must compare and contrast an individual's test results against the results of a large pool of others who have taken the same test. However, the individual may belong to a different age group or culture than the majority of the "norm group," or differ from the norm in some other way, says Groth-Marnat, making these comparisons potentially less reliable.

Evaluator's Training

Furthermore, all psychological tests must be interpreted by a subjective human being who may inadvertently introduce human error. Groth-Marnat stresses that the evaluator might need to undergo training in order to accurately interpret a particular test.

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