Re: a different test scoring policy?

["Michael Porter" <mporter@storm.ca>]

James Mclean wrote:

> I recently had an nebulous idea on a test scoring strategy to discourage
> blindly applying equations (perhaps chosen simply because the symbols
> match), rather than thinking through the physics.  The basic idea is to
> *subtract* points when this occurs.  That is, a really botched problem
> could actually garner a negative score.

Are you afraid that the students are getting some problems _right_ because
they happened to guess correctly which equation to use?  I am assuming this
is the case, since a negative score serves to take points away from other
problems that the students have gotten right.

This reminds me of the (multiple choice) contests my students write, in
which correct answers are given one point, and incorrect answers are given
-0.25 points.  Theoretically, a completely random guesser would get a score
of zero on the contest.

I don't think it is necessary to apply this rule to a test.  Since anything
under a 50 is a failure anyway, students that rely too much on guessing will
not succeed even if they do collect the odd mark for guessing correctly. 
Also, you may be discouraging students who think they know how to do a
problem, but are not totally sure which equation to use; or want to
experiment with a likely equation and see if the answer is reasonable.

If a student picks the wrong equation, give them a zero and leave it at
that.  I _have_ given a mark in cases where the student did this, got an
unreasonable answer, but was able to explain why (e.g. "This wavelength
can't be right since the visible spectrum ranges from 400-700 nm").  In this
case, the student is thinking physics, just not enough to pick the right
equation.

Mike

Michael Porter
Colonel By Secondary School
Gloucester, Ontario Canada

mporter @ storm . ca