Sixia Chen, PhD, Assistant Professor of Biostatistics. Dr. Chen has extensive experience related to statistical methods development in missing data and survey research methods. He has worked as a collaborative and methodologic statistician in the Center for Survey Statistics and Methodology at Iowa State University as a Graduate Research Assistant, as a Statistical Analyst in Mathematica Policy Research for 3 months and more recently, as a Senior Survey Statistician at Westat, where he gained experience in statistical consulting for sample design, weighting, and imputation. He has been productive in developing new statistical methods related to sampling and inference in survey studies. He has the expertise necessary to develop sampling plans for complex surveys and to calculate sampling weights that are utilized in the data analysis. Dr. Chen will develop the sampling plan relative to the aims of the investigators, will draw the random sample and will create the sampling weights.