Amelia II performs multiple imputation, a general-purpose approach to data with missing values. This method creates multiple "fill in" or rectangularized versions of the incomplete data set so that analyses which require complete bservations can appropriately use all the information present in a data set with missingness. Multiple imputation has been shown
to reduce bias and increase eciency compared to listwise deletion. Furthermore, ad-hoc methods of imputation, such as mean imputation, can lead to serious biases in variances and covariances. Unfortunately, creating multiple imputations can be a burdensome process due to the technical nature of algorithms involved. Amelia II provides users with a simple way to create and implement an imputation model, generate imputed datasets, and check its fit using diagnostics.