Abstract
of a presentation at Innovation
2008, April 14-15, Breckenridge CO, USA
( Listen to webcast
of this paper, Download Power
Point Presentation )
Certainty-Based Marking: rewarding good judgment of what is or is not
reliable
Tony
Gardner-Medwin
Dept.
Physiology, UCL, London WC1E 6BT
Abstract:
Certainty-Based
Marking (CBM) scores an objective test (usually on a computer) in a way
that rewards students for identifying and distinguishing when
individual answers are reliable or unreliable. It penalises confident
errors and rewards a thoughtful and realistic appraisal by the student
of the basis and limitations of his/her knowledge. It has long been
known to stimulate learning and improve assessment, but is nevertheless
little used in schools or universities. Why not? Before the computer
age there were technical barriers. Some forms of CBM have been too
complex, or have failed to motivate true reporting of uncertainty.
Also, teachers have sometimes confusingly thought CBM rewards
self-confidence, which it does not : it rewards reliable answers, and
good judgment of reliability.
Nowadays CBM is
not only easily implemented (see e.g. www.ucl.ac.uk/lapt), but all the
more essential because of the easy access to information on the
internet. This has turned the role of knowledge assessment somewhat on
its head. Lack of knowledge is no longer such a problem : you can look
it up. What is important is to acknowledge uncertainty, and to
eradicate confident misconceptions that lead to complacency, confusion
and danger. Though information is still crucial, education is more
about handling information than having information. For students who do
well in objective tests without much thinking - perhaps even without
understanding what they have learned - CBM raises the stakes. It forces
them to think more about how their knowledge knits together - whether
it forms the consistent web that we call understanding.
Experience in
London with a simple form of CBM has proved popular with students in
their study and beneficial to student-teacher interaction. Students
need practice to become familiar with the mark scheme, but it rewards
realism in a pedagogically sound manner and improves the statistical
quality of exam data by marking unconfident answers without penalty but
with reduced weight. It avoids two of the cardinal crimes of
assessment: rewarding lucky guesses as if they were knowledge, and
treating confident misconceptions as no worse than acknowledged
ignorance. CBM deserves a much bigger place in the future.