Manipulation of nearly 16 million individual samples of scores and more than 8 trillion individual scores on commonly used tests, including civil service and other pre-employment exams and university entrance exams, has revealed that the tools used to check tests of "general mental ability" for bias overwhelmingly and repeatedly missed the bias inserted in the data. In other words, we’ve been testing potential test bias with a biased procedure.
 . Revival of Test Bias Research in Preemployment Testing. Journal of Applied Psychology [Internet]. 2010 ;95(4):648 - 680. Available from: http://www.sciencedirect.com/science/article/B6WY3-50HVXJ9-4/2/fa394d406a7ce40c85794867ac5b1a98