What is the difference between missing completely at random and missing at random?
The terminology describing missingness mechanisms is confusing. In particular the meaning of 'missing at random' is often misunderstood, leading researchers faced with missing data problems away from multiple imputation, a method with considerable advantages. The purpose of this article is to clarify how 'missing at random' differs from 'missing completely at random' via an imagined dialogue between a clinical researcher and statistician.
Department of Non-communicable Diseases Epidemiology, London School of Hygiene and Tropical Medicine, London, UK krishnan.bhaskaran@lshtm.ac.uk.
Krishnan
K
Bhaskaran
Department of Non-communicable Diseases Epidemiology, London School of Hygiene and Tropical Medicine, London, UK.
Liam
L
Smeeth
D003627:Data Interpretation, Statistical; D006801:Humans; D012107:Research Design; D013223:Statistics as Topic
missing at random; missing data; multiple imputation