Andrew Mercer is a senior research methodologist at Pew Research Center. He is an expert on probability-based online panels, nonprobability survey methods, survey nonresponse and statistical analysis. His research focuses on methods of identifying and correcting bias in survey samples. He leads the Center’s research on nonprobability samples and co-authored several reports and publications on the subject. He also served on the American Association for Public Opinion Research’s task force on Data Quality Metrics for Online Samples. He has authored blog posts and analyses making methodological concepts such as margin of error and oversampling accessible to a general audience. Prior to

joining the Center, Mercer was a senior survey methodologist at Westat. He received a bachelor’s degree in political science from Carleton College and master’s and doctoral degrees in survey methodology from the University of Maryland. His research has been published in Public Opinion Quarterly and the Journal of Survey Statistics and Methodology.