How Tests Measure Psychological Traits Tests enable us to measure psychological traits just as yardsticks and bathroom scales help us measure physical traits. Imagine you are the manager or head coach of a professional basketball team. You have recruiters who go to college and university games and look for players to hire for your team. No doubt, you'd appreciate the measures provided by the second recruiter. His measurement facts take the subjective bias out of his information, making it easier for you to trust his statements.
Humans vary on psychological traits just as they do on physical ones.
Some of us are tall, some short. Some are heavy, some light in weight. Some can run fast and are well coordinated, some are slower and clumsier. When hiring basketball players, height, speed and coordination are critically important. Similarly, when hiring employees, traits such as mental aptitude, conscientiousness and knowledge of basic math and typing are often extremely important to success on the job.