Someone very smart told me that incompetence is a form of bias all of its own, because it privileges people who are able to ask for corrections in their favor.

Someone very smart told me that incompetence is a form of bias all of its own, because it privileges people who are able to ask for corrections in their favor. (They had a nice worked example involving exam results - some years have much higher variance than others, due to incompetence in question-setting or marking, and in those years the mis-marking is randomly distributed but only the more middle class parents manage to work the system to get re-marked)