He makes a few assumptions. But he is probably correct within those assumptions. We assume all candidate pools are homogeneous. If all members of a certain sub

He makes a few assumptions. But he is probably correct within those assumptions. We assume all candidate pools are homogeneous. If all members of a certain subset A of a global population P is simply better at a task than any member of another subset B of the global population, we will see that this holds true for members of our sample as well. Thus, members of A in our sample will consistently outperform members of B in our sample. Does this mean there is a bias against A? Well, yes because if there wasn't then there would be fewer members of B or perhaps no members of B in our sample based on this result alone. However, real life is not one-dimensional. Sometimes we need to consider other factors as well.