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The standard error of measurement is a more appropriate measure of quality for postgraduate medical assessments than is reliability: an analysis of MRCP(UK) examinations

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Tighe, Jane, McManus, IC, Dewhurst, Neil G, Chis, Liliana, Mucklow, John·2010·BMC Medical Education

Abstract

Background: Cronbach's alpha is widely used as the preferred index of reliability for medical postgraduate examinations. A value of 0.8-0.9 is seen by providers and regulators alike as an adequate demonstration of acceptable reliability for any assessment. Of the other statistical parameters, Standard Error of Measurement (SEM) is mainly seen as useful only in determining the accuracy of a pass mark. However the alpha coefficient depends both on SEM and on the ability range (standard deviation, SD) of candidates taking an exam. This study investigated the extent to which the necessarily narrower ability range in candidates taking the second of the three part MRCP(UK) diploma examinations, biases assessment of reliability and SEM. Methods: a) The interrelationships of standard deviation (SD), SEM and reliability were investigated in a Monte Carlo simulation of 10,000 candidates taking a postgraduate examination. b) Reliability and SEM were studied in the MRCP(UK) Part 1 and Part 2 Written Examinations from 2002 to 2008. c) Reliability and SEM were studied in eight Specialty Certificate Examinations introduced in 2008-9. Results: The Monte Carlo simulation showed, as expected, that restricting the range of an assessment only to those who had already passed it, dramatically reduced the reliability but did not affect the SEM of a simulated assessment. The analysis of the MRCP(UK) Part 1 and Part 2 written examinations showed that the MRCP(UK) Part 2 written examination had a lower reliability than the Part 1 examination, but, despite that lower reliability, the Part 2 examination also had a smaller SEM (indicating a more accurate assessment). The Specialty Certificate Examinations had small Ns, and as a result, wide variability in their reliabilities, but SEMs were comparable with MRCP(UK) Part 2. Conclusions: An emphasis upon assessing the quality of assessments primarily in terms of reliability alone can produce a paradoxical and distorted picture, particularly in the situation where a narrower range of candidate ability is an inevitable consequence of being able to take a second part examination only after passing the first part examination. Reliability also shows problems when numbers of candidates in examinations are low and sampling error affects the range of candidate ability. SEM is not subject to such problems; it is therefore a better measure of the quality of an assessment and is recommended for routine use.

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Authors
Tighe, J., McManus, I., Dewhurst, N. G., Chis, L., & Mucklow, J.
Affiliations
University College London (GB)
Corresponding author
McManus, IC
Venue
BMC Medical Education
Published
2010-06-02
Volume
10
Issue
1
Pages
40-40
ISSN
1472-6920 (ISSN-L)
OpenAlex
W2110536261
Cited by
113
References
8
Citations by year
2026: 7 · 2025: 15 · 2024: 13 · 2023: 6 · 2022: 9 · 2021: 8 · 2020: 6 · 2019: 7 · 2018: 6 · 2017: 7 · 2016: 3 · 2015: 10 · 2014: 1 · 2013: 5 · 2012: 6
FWCI
4.77
Type
journal article
Language
en
Open access
Locations
  • BMC Medical Education (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • UCL Discovery (University College London) (submittedVersion)
Topics
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Innovations in Medical Education
  • Social Sciences › Decision Sciences › Management Science and Operations Research › Psychometric Methodologies and Testing
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Medical Education and Admissions
Keywords
standard error of measurement, test reliability, Cronbach's alpha, postgraduate medical examination, range restriction, assessment quality, Monte Carlo simulation
MeSH terms
Education, Medical, Graduate, Educational Measurement, Humans, Monte Carlo Method, Reproducibility of Results, Models, Statistical

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