Multiple Imputation Using SAS Software

Abstract

Multiple imputation provides a useful strategy for dealing with data sets that have missing values. Instead of filling in a single value for each missing value, a multiple imputation procedure replaces each missing value with a set of plausible values that represent the uncertainty about the right value to impute. These multiply imputed data sets are then analyzed by using standard procedures for complete data and combining the results from these analyses. No matter which complete-data analysis is used, the process of combining results of parameter estimates and their associated standard errors from different imputed data sets is essentially the same. This process results in valid statistical inferences that properly reflect the uncertainty due to missing values.

This paper reviews methods for analyzing missing data and applications of multiple imputation techniques. This paper presents the SAS/STAT MI and MIANALYZE procedures, which perform inference by multiple imputation under numerous settings. PROC MI implements popular methods for creating imputations under monotone and nonmonotone (arbitrary) patterns of missing data, and PROC MIANALYZE analyzes results from multiply imputed data sets.