I have at various times used tests that are completely "closed," tests
in which students provide their own crib sheet, and tests in which I
provide a crib sheet.
When our students provide their own crib sheets, they tend to cram
onto it every equation they can find, and try to solve problems by
simply looking for equations that have the right variables.
When I provide the crib sheet, students complain when I omit something,
no matter how simple. The straw that broke the camel's back was
when I neglected to include P = E / t (power = energy / time) in a
general physics test that was mainly about electrical circuits.
So now, I use mostly "closed" tests, but try to focus the questions and
problems on basic principles and definitions, and provide complex equations
occasionally. This works fairly well for general physics, modern physics
and optics, but less well for more complex subjects like quantum
mechanics and thermodynamics, where it's hard to come up with "simple"
problems.
--
Jon Bell <jtbell@presby.edu> Presbyterian College
Dept. of Physics and Computer Science Clinton, South Carolina USA