The main objective of EPSO's cognitive ability tests is to measure key reasoning abilities for all future EU officials, not simply to cut down candidate numbers. Based on well-established scientific studies, these tests have the highest predictive value of future job performance (compared to purely knowledge-based tests). Even though candidates within the same competition do not receive the same questions, the level of difficulty of the individual tests delivered to each candidate is identical, thereby ensuring equal treatment. The validity and reliability of multiple-choice computer-based tests has been confirmed by European Court of Justice case-law, and the Court also confirmed that these tests comply with the principle of fair and equal treatment. At the same time computer-based tests allow EPSO to test several tens of thousands of candidates in multiple locations in a very short time (+/- 4 weeks for 30,000 applicants) in an efficient and user-friendly manner as candidates do not have to test all at the same date/time.