Implementation of a National Assessment of Educational Achievement focuses on the practical tasks involved in running a large-scale national assessment program. It has four parts. Part I provides an overview of the tasks involved - how the essential activities of an assessment are organized and implemented, the personnel and resources that are required, and the tasks that follow the collection of data. In Part II, a methodology for selecting a sample of students that will be representative of students in the education system is presented. Principles underlying sampling are described, as well as step-by-step procedures that can be implemented in nearly any national assessment. An accompanying CD contains supporting data files. Part III describes procedures for cleaning and managing data collected in a national assessment, essential elements of a quality assurance process. It also describes how to export and import data, that is, make data available in a format that is appropriate for users of statistical software such as Access, SPSS, WesVar, and Excel. The primary objective of this section is to enable the national assessment team develop and implement a systematic set of procedures to help ensure that the assessment data are accurate and reliable. Following sampling, test administration, data entry, and cleaning, the next step is to prepare data for analysis. In Part IV, a series of important pre-analysis steps, including producing estimates, computing and using survey weights, and computing estimates are described. The section dealing with the computation of estimates describes how they and their sampling errors are computed from simple and complex samples. Finally, a range of special topics, including nonresponse and issues relating to over-and under-size schools, is addressed.