Re: A misapplication of probability theory in exam grading

pauldepstein@xxxxxxx wrote:

jankrihau@xxxxxxxxxxx wrote:
...
Hi,

I don't think it was an attempt to remove randomness, but rather to
arrange so that random guessing doesn't score better than not
answering. Hence the choice of (-1, 4): It gives the expected value 0
for random guessing. Although there is still an element of randomness,
the expected score for the whole test becomes 4 x the number of
questions the candidate actually knew the answer to, regardless of
whether he or she made random guesses or chose to leave some questions
unanswered.

---
J K Haugland
http://home.no.net/zamunda

If you want the expected score of random guessers to be 0, you don't
need to fuss with silly rule changes in this way. You can just use the
normal system and then do a final subtraction of (number of
questions)/5.

I don't know why you use the tentative formulation "still an element"
of randomness.

My whole point is that the penalty system (when used optimally by
students) has _exactly the same_ degree of randomness as the more
traditional no-penalty system.

The penalty-system was introduced with a completely dishonest and
fallacious propaganda campaign that the new system is "fairer" and
removes some randomness. It does absolutely nothing of the kind.


It's probably because subtracting points from the total score confuses
people more than giving negative scores for incorrect answers. For
example, let's say there are ten questions. In the first case, one
point is awarded for a correct answer, zero for an incorrect answer,
and then two points are subtracted from the total score. This raises
the obvious question in the sitter's mind: "why on earth are two points
being subtracted?" The other option - four points for a correct answer,
one point deducted for incorrect - probably makes more sense to most
people, without the need of any complicated explanation.

.

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