Transcription of Missing-data imputation - Department of Statistics
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Missing-data imputation - Department of Statistics
CHAPTER 25 Missing-data imputationMissing data arise in almost all serious statistical analyses. In this chapter wediscuss a variety of methods to handle missing data , including some relatively simpleapproaches that can often yield reasonable results. We use as a running example theSocial Indicators Survey, a telephone survey of New York City families conductedevery two years by the Columbia University School of Social Work. Nonresponsein this survey is a distraction to our main goal of studying trends in attitudes andeconomic conditions, and we would like to simply clean the dataset so it could beanalyzed as if there were no missingness. After some background in Sections , we discuss in Sections our general approachof random discusses situations where the Missing-data process must be modeled(this can be done in Bugs) in order to perform imputations data in R and BugsIn R, missing values are indicated by NA s.
Two problems arise with complete-case analysis: 1. If the units with missing values differ systematically from the completely ob-served cases, this could bias the complete-case analysis. 2. If many variables are included in a model, there may be very few complete cases, so that most of the data would be discarded for the sake of a simple analysis.
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