The decennial census is foundational to the functioning of American democracy, and maintaining the public's trust in the census and its resulting data is a correspondingly high-stakes affair. The 2020 Census was implemented in light of severe and unprecedented operational challenges, adapting to the COVID-19 pandemic, natural disasters, and other disruptions. This interim report from a panel of the Committee on National Statistics discusses concepts of error and quality in the decennial census as prelude to the panel's forthcoming fuller assessment of 2020 Census data, process measures, and quality metrics. The panel will release a final report that will include conclusions about the quality of the 2020 Census and make recommendations for further research by the U.S. Census Bureau to plan the 2030 Census.Table of ContentsFront MatterSummary1 Introduction2 Frameworks for Understanding the Decennial Census and Its Quality3 Other Evaluations of the 2020 Census4 Initial Conclusions and the Path AheadReferencesAppendixesAppendix A: Glossary and AbbreviationsAppendix B: Public Meeting AgendasAppendix C: Biographical Sketches of Panel Members and StaffCommittee on National Statistics