Chapter 5: TIMSS 2007 Sample Design

5.1 Overview this chapter describes the tiMSS 2007 sample design, which consists of a set of specifications for the target and survey populations, sampling frames, survey units, sample selection methods, sampling precision, and sample sizes. the sample design is intended to ensure that the tiMSS 2007 survey data provide accurate and efficient estimates of national student populations. Since measuring trends is a central goal of tiMSS, the sample design also aims to provide accurate measures of changes in student achievement from cycle to cycle. in addition to the sample design, the tiMSS 2007 sampling activities also include estimation procedures for sample statistics and procedures for measuring sampling error. these other components are described in chapters 9. the basic tiMSS sample design has two stages: schools are sampled with probability proportional to size at the first stage, and one or more intact classes of students from the target grades are sampled at the second stage. all participants followed the uniform sampling approach specified by the tiMSS 2007 sample design with minimum deviations. this ensured that high quality standards were maintained for all participants, avoiding the possibility that differences between countries in survey results could be attributable to the use of different sampling methodologies. this uniform approach also facilitated an efficient approval process of the national designs by the international project team. the tiMSS 2007 national Research coordinator (nRc) of each participating country was responsible for implementing the sample design, including documenting every step of the sampling procedure for approval by the tiMSS & PiRLS international Study center prior to implementation. to support nRcs in their sampling activities, a series of manuals: the TIMSS 2007 School Sampling Manual, TIMSS 2007 Survey