Volume 21, Issue 4 (Vol.21, No.4, Winter 2026)
irje 2026, 21(4): 346-365 |
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Amjadi Zin Hajloo P, Heidari M. Missing Data in Medical Research: A Practical and Illustrated Review for Researchers and Students. irje 2026; 21 (4) :346-365
URL: http://irje.tums.ac.ir/article-1-7531-en.html
URL: http://irje.tums.ac.ir/article-1-7531-en.html
1- Master of Epidemiology, Department of Epidemiology and Biostatistics, School of Medicine, Urmia University of Medical Sciences, Urmia, Iran
2- Assistant Professor of Epidemiology, Department of Epidemiology and Biostatistics, School of Medicine, Urmia University of Medical Sciences, Urmia, Iran ,heidari.m@umsu.ac.ir
2- Assistant Professor of Epidemiology, Department of Epidemiology and Biostatistics, School of Medicine, Urmia University of Medical Sciences, Urmia, Iran ,
Abstract: (23 Views)
Missing data is a common and unavoidable challenge in medical and epidemiological research, often leading to biased estimates, reduced statistical power, and misleading interpretations when not properly addressed. Despite its importance, accessible and practical educational resources on this topic remain limited in Persian. This educational article provides a clear and structured overview of the fundamental concepts of missing data, including definitions, common patterns (univariate and multivariate), and the three major mechanisms of missingness: MCAR, MAR, and MNAR. A range of widely used approaches for handling missing data is summarized, from basic methods such as case deletion and simple imputation to more advanced techniques including multiple imputation and likelihood-based procedures (EM and MLE). Practical examples and visual illustrations are incorporated to facilitate conceptual understanding. The ultimate goal of this article is to provide a practical framework for researchers and students, enabling them to select the appropriate approach for dealing with missing data in the design and analysis of their research and to prevent analytical errors.
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