[proveanegative]

If candidates from group A perform more strongly on average than those from group B there are other possible causes than bias in the selection process itself. For instance, members of group A may only apply at a higher level of self-assessment for how likely they are to succeed than those in group B. The reason for this could be opportunity cost not present for group B, overconfidence or lack of underconference in group B or underconference or lack of overconfidence in group A.