A reappraisal of the use of the phi‐coefficient in multiple choice examinations
作者:
J. H. KOESLAG,
S. R. SCHACH,
C. W. MELZER,
期刊:
Medical Education
(WILEY Available online 1987)
卷期:
Volume 21,
issue 1
页码: 46-52
ISSN:0737-3805
年代: 1987
DOI:10.1111/j.1365-2923.1987.tb00513.x
出版商: Blackwell Publishing Ltd
关键词: * Statistics;educational measurement/*methods;*education;medical;undergraduate;physiology/educ;pharmacology/educ;anatomy/educ;South Africa
数据来源: WILEY
摘要:
Summary.The phi‐coefficient of an item in a multiple choice question (MCQ) examination is often used to determine whether that item is suitable for re‐use in future examinations. In order to be of value in this regard, the coefficient must be shown to be an objective and consistent index of the discriminating power of an MCQ item. The behaviour of the phicoefficient (ø) was investigated in two one‐from‐five MCQ and two true/false examinations. It is shown that the magnitude of the ø‐coefficient for the items in any examination is a function not only of the discriminating power of the items, but also of the magnitude of the countermark for incorrect responses, of the proportion of‘don't know’ responses in the examination, and of how the‘don't know’ responses are handled in the analysis. It is further shown that the reproducibility of the ø, when calculated for any pair of randomly selected portions of a class of students, is very poor. We conclude that the error of estimation of the ø is of the same order of magnitude as the ø's
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