This might be a good example of "sample bias" for those studying for their Statistics exam.

Those most likely to have seen this poll are probably self-selected for higher than average success on exams. The fact that they know about this forum already gives them an advantage. And those who have failed a lot of exams probably aren't hanging around here anymore. And even if they are, they may be too embarrassed to answer the poll (even though it's anonymous).

-Gary-