Hello,
The criteria used should be objective, relevant to the job in question and capable of being applied fairly to all concerned without bias.
If a job requires you to have two legs and you are deficient to the tune of one leg, then this is an objective criteria upon which your ability to perform in that job could be reasonably assessed in comparason to someone who had, say, two legs.
If you are follicly challenged, and this has no bearing on your ability to perform the work that you are expected to do, assessment on this criteria could be said to be subjective.
Frank puts it very well, the criteria should be such that there is no discrimination in its application.
Regards,
Recycled.