Imputation as an approach to missing data has been around for decades.
You probably learned about mean imputation in methods classes, only to be told to never do it for a variety of very good reasons. Mean imputation, in which each missing value is replaced, or imputed, with the mean of observed values of that variable, is not the only type of imputation, however. (more…)
You may have never heard of listwise deletion for missing data, but you’ve probably used it without knowing it. Even when it doesn’t work well. 
Listwise deletion means that any case in a data set is deleted from an analysis if they’re missing data on any variable in the analysis.
It’s the default in most statistical software packages.
Although its simplicity is a major advantage, it causes big problems in many missing data situations.
But…not always. If you happen to have one of the uncommon missing data situations in which (more…)
One important consideration in choosing a missing data approach is the missing data mechanism—different approaches have different assumptions about the mechanism.
Each of the three mechanisms describes one possible relationship between the propensity of data to be missing and values of the data, both missing and observed.
Missing Completely at Random, MCAR, means there is no relationship between (more…)