Three issues impeding communication of statistical methodology for incomplete data

Abstract: We identify three issues permeating the literature on statistical methodology for incomplete data written for non-specialist statisticians and other investigators. The first is a mathematical defect in the notation Yobs, Ymis used to partition the data into observed and missing components. The second are issues concerning the notation `P(R|Yobs, Ymis)=P(R|Yobs)' used for communicating the definition of missing at random (MAR). And the third is the framing of ignorability by emulating complete-data methods exactly, rather than treating the question of ignorability on its own merits. These issues have been present in the literature for a long time, and have simple remedies. The purpose of this paper is to raise awareness of these issues, and to explain how they can be remedied.