Data Quality Assessment begins by reviewing the Data Quality Objectives (DQO) Summary Report (Chapter 3, Section 3.2.6), Sampling and Analysis Plan (Chapter 3, Section 3.2.7), Quality Assurance Project Plan, and any related documents. Reviewing these documents provides the context for understanding the purpose of the data collection effort and establishes the qualitative and quantitative basis for assessing the quality of the data set for the intended use. The sampling design presented in the Sampling and Analysis Plan provides important information about how to interpret the data. By studying the sampling design, the reviewer can gain an understanding of the assumptions under which the design was developed, as well as the relationship between these assumptions and the study objective. By reviewing the methods by which the samples were collected, measured, and reported, the reviewer prepares for the preliminary data review and subsequent steps of Data Quality Assessment (EPA 2006a).