alt Hacker News> How else would you define bias if not an offset from equality or zero mean?
As an offset from what the ground truth justifies. Suppose the researchers had decided to load the dice when creating the fake sample data; an unbiased analyst should seek to discover the extent of that, not insist on reporting equality.
Well, in this study, they explicitly had equality - all four groups were as likely to succeed. So any difference in hiring was actual bias (or statistical noise).