Power calculation in multiply imputed data

Multiple imputation (MI) has been proven an effective procedure to deal with incomplete datasets. Compared with complete case analysis (CCA), MI is more efficient since it uses the information provided by incomplete cases which are simply discarded in CCA. A few simulation studies have shown that statistical power can be improved when MI is used. However, there is a lack of knowledge about how much power can be gained. In this article, we build a general formula to calculate the statistical power when MI is used. Specific formulas are given for several different conditions. We demonstrate our finding through simulation studies and a data example.