Company XYZ is using an aptitude test to measure the applicants’ cognitive abilities. The score of the test can vary from 10 to 100. A score of 10 indicates very low cognitive abilities whereas a score of 100 indicates exceptional cognitive abilities. A job candidate, Robert, received a score of 87 when he took the test in April. Robert took the test again (same test) in June. However, the second time his score was only 42. What type of problem may this test have?