Certainty-Based Marking (CBM)
Confidence- or certainty-based assessment in various guises has a long history, and is surprisingly under-used. When properly set up, it motivates students to think carefully about whether they can see reasons for either sound justification or uncertainty about the answers they give in tests. It is particularly helpful as a study aid in self-tests, providing a stimulus and challenge, and a warning signal when misconceptions have arisen. But it has also been clearly shown to improve the statistical reliability and validity of assessment data.
I implemented CBM at UCL in 1994 for my own teaching in physiology, medicine and maths. The principles and outcomes are set out in my teaching publications. UCL nowadays mainly uses Moodle (where I also incorporated CBM in 2013), but for CBM self-tests I prefer the more versatile software that I developed for UCL and that is now hosted here following my retirement in 2006. In the 10 years 2015-2025 a total of 135,000 anonymous self-test CBM sessions were recorded - probably mostly for UCL students - to supplement their formal course material.
CBM Self-Tests
This CBM Self-Test site evolved from software at UCL called LAPTTOP ("London Agreed Protocol for Teaching and Testing of Physiology"), then later LAPT after usage branched out to include Anatomy, Medical Science, Maths & Physics. It enables students to do private study, choosing questions or exploring unfamiliar topics without their mistakes featuring in their record. Comments and questions about issues can be entered in context, with options for staff notification when these arise so they can reply or edit material. Students learn through their mistakes, their careful thinking, and through working jointly with friends. Display of new questions and responses to answers appear immediately, without requiring online interaction - to assist efficient learning. As a corollary of this though, the software is not suitable for high-stakes assessment since answers as well as questions are held in files on the student computer, and could in principle be misused.
Using CBM in Moodle
CBM has been implemented in core Moodle code since version 2.6 (2013), see Using certainty-based marking in Moodle. For full CBM staff reports, it is essential to install the appropriate CBM Grades PLUGIN. In addition, there are downloadable code modifications available here that substantially enhance CBM performance and feedback to students compared with core code up to the present. These code mods are also available to fully implement CBM as far back as v1.9. Each download contains a few files to replace core Moodle files in an appropriate version. No adverse events have been reported from installing any of these downloads, and the changes can be easily reversed by overwriting altered files with the supplied original versions. Please do report any problems to me.
Links (opening in a separate window or tab)
Any comments, suggestions or questions: please don't hesitate to email.
Prof. Tony Gardner-Medwin
Emeritus Prof. of Physiology, UCL Div. of Bioscience
ucgbarg@ucl.ac.uk