Below is a comment from The Reading Workshop, on the post The Life of a Test Grader. To be truthful I think that post is a worst case possibility.(It is not 100% the same as my other comment, a few words have been changed.)
I think if someone had a morning that bad I think anyone could get a bad test score. I know if my mom ever had a morning that bad, she wouldn’t go to work. Really it would matter what kind of person graded my test. If it’s a super specific person that wants the wording to be 100% the same then almost everyone would get a bad score, but if it’s a person that’s not like that and had good morning then people would not miss as many points.
The worst possible thing that could happen would be that a super specific person who had a really bad morning (Like Martha’s morning.) would probably give much fewer points. Really how many points some one would get would be a combination of what kind of person graded your test and how good/bad their morning was.