Many psychological tests are difficult to administer. According to Rider University, properly giving and grading a psychological test is considered a graduate level skill. Undergraduates learn about tests, such as the Rorschach ink blot test and the Minnesota Multiphasic Personality Inventory, but they do not have the statistical knowledge to properly interpret the results. Performing the test requires knowledge about how statistical concepts such as a t-score relate to the validity of the test results.
Some psychological tests are only effective because their methods are secret. The test giver will invalidate the test if the material on the test becomes known to the public. Employees who have prior knowledge about the questions on an exam, such as a psychological survey an employer requires, can provide the answers the employee thinks the employer wishes to receive. According to Loyola University, Chicago, many test materials are stored in secure locations and can only be accessed by qualified psychologists.
Test providers may charge a fee to administer the test. Valid tests are designed by such professionals as psychologists, statisticians and other psychometric experts, who commonly have graduate degrees. Many tests are under copyright and may not be used without permission from a testing center, or the psychologist who created the test. Using a test without permission or sharing its details with the public may violate intellectual property law. According to the American Psychological Association, publishers may refuse to sell access to a test to anyone who cannot show credentials that prove she can properly administer and grade the test.
A controlled environment is necessary to administer a psychological test. According to Loyola University, Chicago, a psychology professor should supervise students while they administer psychological tests. A supervisor must carefully control the environment in the test center. Performing a psychological test over the phone or at an employee's home computer does not provide much control, compared to a test center where outside materials are banned and test takers cannot communicate with one another.