|
CBM: teachers
How Does It Work
CBM marks a student according to confidence (or 'degree of certainty') in each answer.
|
Confidence level : |
C=1
(low)
|
C=2
(mid)
|
C=3
(high)
|
No Reply
|
|
Mark if correct :
|
1
|
2
|
3
|
(0)
|
|
Penalty if wrong :
|
0
|
- 2
|
- 6
|
(0)
|
Such a
scheme rewards students who reflect to the
point that they can either :-
(a) justify high confidence so that they are prepared to risk a penalty if wrong,
or
(b) identify reasons for reservation so that they lower their confidence
and
eliminate risk.
Both ways
they gain by thinking more deeply and by correctly judging reliability.
A
student who distinguishes reliable from uncertain areas of knowledge
does
better than one with the same number of correct answers who cannot
judge this
correctly.
CBM discriminates more
significant levels of knowledge
than does mere correctness. Roughly :
3 = knowledge 2 = uncertainty 1,0 = ignorance -2 = misconception -6 = delusion! or
3,2 = usable knowledge 0,1 = unusable
knowledge -2,-6 = dangerous knowledge
In assessment, CBM
weights uncertain answers less than
confident ones. This reduces the variance due to 'guessing' and
increases the
statistical reliability of exam results, as shown in several research
studies
and borne out in analysis of exam data at UCL. CBM scores have been
found to be
the best predictors even of the % correct on a separate set of
questions.
Practical Issues
·
CBM can be used wherever
objective testing (right/wrong answers) is used (e.g.
T/F , MCQ , EMQs
,
numerical , word/phrase answers)
·
It does not require a
special
style of question setting.
·
Objective Testing is not just
about factual knowledge.
·
Exercises can be set up with WebCT,
with authenticated student grades returned to the VLE.
·
Question files are easily
adapted from any systematic text/graphic/HTML format using the
exercise specification manual, and can be
drafted in WORD or (for easy application of flexible
arrangements for different formats, conditional explanations, etc.) with a
dedicated authoring tool on the website.
·
Exercises (for formative
use
without recording of data) can be run from a CD-ROM or local drive.
·
For summative
exams, till your experience may inform new strategies, provisional
passmarks can always be set by reference to the number passing on
conventional
criteria (% correct answers).
·
Help,
advice, troubleshooting and adaptations
are all freely available from UCL (cusplap@ucl.ac.uk).
Tony
Gardner-Medwin -- Physiology,
UCL -- (ucgbarg@ucl.ac.uk)
or Reid Cornwell, Director TCFIR wrc@tcfir.org
|