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Computer Based Testing of Medical Knowledge. Tom Mitchell, Nicola Aldridge Intelligent Assessment Technologies Ltd. Walter Williamson Faculty of Medicine,

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Presentation on theme: "Computer Based Testing of Medical Knowledge. Tom Mitchell, Nicola Aldridge Intelligent Assessment Technologies Ltd. Walter Williamson Faculty of Medicine,"— Presentation transcript:

1 Computer Based Testing of Medical Knowledge. Tom Mitchell, Nicola Aldridge Intelligent Assessment Technologies Ltd. Walter Williamson Faculty of Medicine, University of Dundee. Peter Broomhead Brunel University.

2  Project carried out in Medical School at Dundee University in autumn 2002 / spring 2003.  Computerisation of an existing paper-based test of medical knowledge.  Test comprised of 270 short-answer free-text items.  Marking of the paper-based tests consumed unsustainable amount of faculty resources.  Computer system developed and rolled-out for 2003 tests. Overview.

3 The GMC defines “core” knowledge which is essential for a medical student.  The Medical School at Dundee has implemented this by teaching to 12 learning outcomes.  Assessment of the course involves written and practical tests.  The GMC review team rated Dundee “Excellent”, but also recommended a new assessment to improve student feedback and course audit : A Progress Test. Background

4 What is a Progress Test ?  A comprehensive assessment of medical knowledge.  Inform students about their year-on-year progress against learning outcomes.  Highlight gaps in their knowledge, and their performance relative to their peers.  At Dundee the Progress Test is administered annually throughout the five years of the undergraduate programme – each year group sits same test. Progress Tests.


6 Piloted in April / June 2001.  Test designed by Professor M. Friedman.  MCQ discounted :  Testing recall of knowledge, not recognition.  “A doctor does not get five choices.”  Many US schools moving to open-ended format.  The first test comprised 250 short-answer free- text items. Longer term aim is to build up a bank of items. The Dundee Progress Test.

7 Items are short-answer free-text text.  What simple clinical test can distinguish between solid and cystic scrotal swellings ?  Accept : Transillumination, shining light through swelling.  Allow: Light goes through cyst.  Don’t accept on own: shine light at/on/behind… Progress Test Items (1).

8 1 transillumination of the area with a light source in a darkened room, cystic lesions will transilluminate but solid ones wont. 1 shine a light through it - cystic lesions allow light through, solid lesions don't 1 Illumination - can light pass throught the swelling - cystic if it does 1 shine a torch behind the swelling. cystic swelling will transilluminate 1 using a torch to shine a light through the swelling 1 Tranillumination of the scrotum with a torch 1 trans illumination of the scrotal swelling 0 using a pen torch to illuminate the swelling 0 illumination of the swelling using a light source Progress Test Items (2). Free-text text responses…

9  150+ students per academic year, 750 - 800 students in total.  3 hour test, 250 – 270 short-answer free-text items.  Admin : Print, collation, etc. of different 30 page test booklets (items in different order), test admin, script storage etc.  Marking : 800 scripts, 750 x 240 = 180,000 items to mark + data entry, rapid feedback required.  Plus, moderation of marking guidelines required. Paper-Based Testing (1).

10 Moderation  To achieve consistent marking, the marking guidelines must be moderated in light of real student responses.  Approach at Dundee was to use Year 5 marking process to moderate marking guidelines.  Group of senior academics mark Year 5, the resulting marking guidelines are used to mark all other years by a team of 6 markers. Paper-Based Testing (2).

11 Problems with the paper-test.  Moderation. Script-by-script marking is tedious and inefficient way to moderate marking guidelines, and required significant time element from senior academics.  Marking. ≈160 scripts per year group, a team of 6 markers can together mark around 15 scripts per hour. ≈ 30 man-days just to mark scripts.  Admin. Data entry for 180,000 marks.  Feedback. Due to the intensity of work required, timely feedback was not achieved. Conclusion : Paper-based progress test was “unsustainable”. Paper-Based Testing (3).

12 Computerised pilot ran in autumn 2002 :  To assess the reaction of the students to a computerised progress test;  To examine the accuracy of computerised marking for progress test items;  To contribute towards defining the specification of a full system. The pilot system used IAT’s free-text marking engine, AutoMark (see 2002 CAA paper). A Computerised Pilot (1).

13 How do we mark free-text responses by computer ?  IATs Marking Engine does not operate on raw text, but on the output of a sentence analyser. Computerised Marking

14 How do we represent the mark scheme ?  Each mark scheme answer is represented as a template.  Each template specifies one particular form of acceptable or unacceptable answer. A Computerised Mark Scheme

15 Computerised Mark Schemes.

16 The Pilot.  Computerised mark schemes were developed for 25 items used in previous years’ progress tests.  An online test comprising the items was delivered to approximately 30 students in November / December 2002.  Student responses were computer marked, and the marking accuracy analysed.  The error in computerised marking was ≈ 1%.  Student feedback from the pilot was positive. A Computerised Pilot (2).

17 A Computerised Progress Test.

18 Test Delivery.

19 Computerised Marking (1).

20 Computerised Marking (2).

21 Computer- Assisted Moderation (1).

22 Computer- Assisted Moderation (2).

23 Subsequent to moderation of marking guidelines.  Where necessary, computerised mark schemes were re-worked.  Any outstanding tests were re-marked, and the results output.  The re-worked computerised mark schemes are now considered “moderated”, and can be used to mark future tests with a high level of confidence. After Moderation.

24 The academics’ view :  Being able to view all student responses to an item together is a major advantage.  The process of moderation via computer is actually a positive experience for academics – could lead to better item writing.  On-screen moderation was quicker than expected, responses could be scanned quickly, and most items required little input  Computer-assisted moderation is a significant improvement over the previous “ordeal”. Conclusions on Moderation.

25 Data from Year 5 Moderation.  5.8% of marks changed by moderators.  Most (4.2%) due to omissions in original marking guidelines or problems in item wording.  Only 1.6% due to errors in computerised marking. After Re-Working the Comp. Mark Schemes.  Agreement between moderated marks and computerised marking 99.4% for Year 5.  0.6% error due to system errors in marking engine. Accuracy of Marking (1).

26 Responses from 10 Year 2 and Year 3 students selected at random, and hand marked. Accuracy of Marking (2). Number of Students Affected Marks Gained / Lost by Hand Marking 50 4+1 (0.37%) 1+2 (0.74%) Mean error from the sample was 0.22%, highest error 0.74%

27 As a further check, 4 Year 5 students chosen.  Two who had unexpectedly over-performed, two who had unexpectedly under-performed.  Responses hand marked.  No discrepancies between human and computer marking encountered. Accuracy of Marking (3).

28 Hand-marking the progress test is onerous.  800 scripts, 270 items per script, a team of 6 markers can mark approx 15 scripts per hour.  The error in hand marking has been measured at between 5% and 5.5% (two studies).  This is comparable with unmoderated computerised marking (5.8%).  Moderated computerised marking is significantly better - of the order of 1%. Human vs. Computerised Marking.

29 Advantages of the computerised system include:  Moderation less painful, and more productive.  After sample-based moderation, re-marking takes hours, not weeks of work.  For this test, marking accuracy is actually improved.  Production of reports automated, data entry not required.  Moderated items can be re-used in future tests.  Flexibility of test-taking is greatly increased. Conclusions (1).

30 The model of computerised marking and computer-assisted moderation can benefit CAA.  Enables use of educationally valued free-text items.  “Credibility-gap” addressed – marking can be checked and moderated on a sample of the cohort.  Enables banks of moderated free-text items to be assembled.  Moderation process benefits item-writing – better assessment, not just better CAA. Conclusions (2).

31 Project :  Complete testing of remaining 150+ students.  Add new items for next year’s tests. Technology :  Enable item writers / academics to create, test, and modify computerised mark schemes.  Integrate marking / moderation functionality with QuestionMark Perception. Future Work.

32 Computer Based Testing of Medical Knowledge.

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