When I was in the security clearance process, the first step in the process was a 500 question multiple choice psychological exam (randomized order). The test is designed to have some level of error checking to make sure participants are taking it seriously (e.g. questions that would be expected to correlate). Near the start of the exam was a question "do you have back pain", I answered "no". Near the end was the same question phrased slightly differently, I answered "yes". When in my subsequent interview to discuss the results, the interviewer questioned why I didn't answer consistently. She seemed to accept my answer of "I had been sitting in an uncomfortable chair for 2.5 hours by the time I got to the second question".