The U.S. TIMSS data files are made available in three versions. The differences between these versions are summarized in the following table and described in detail below it. TIMSS data files are quite complex on account of the study’s multi-stage sample design and use of imputed scores (also known as plausible values); these complexities can make analyzing the data challenging. To help users explore the TIMSS data, we have compiled a list of NCES and external online tools and tutorials focused on TIMSS on the Analyzing Tools web page.
Table 1: Comparing three versions of the U.S. TIMSS data files for each cycle
|19952, 1999, 2003, 2007, 2011, 20152||
1 Starting with the 2019 cycle, the U.S. national public-use data files are considered add-on files because they do not contain international variables, such as plausible values, sampling variables, and weighting variables; therefore, they must first be merged with the international U.S. data files before any analyses can be conducted.
2 The 1995 and 2015 cycles also include TIMSS Advanced data files.
1. TIMSS International U.S. data files
The U.S. international data files are part of the TIMSS international database, which is available for download for each round of TIMSS from the TIMSS and PIRLS International Study Center website. The U.S. data files in the international database are directly comparable to the data files of the other participating education systems. The content and structure of the international database and its supporting documents are described in detail in the international user guide. Briefly, the international database includes the “international” variables such as student achievement data; estimated achievement scores (i.e., plausible values); questionnaire data from students, teachers, and schools; curriculum data; and sampling and weighting variables.
2. TIMSS U.S. national public-use data files (PUFs)
The main purpose of the U.S national public-use data files (PUFs) is to provide access to U.S.-specific variables that are not available in the U.S. international data files. For example, the additional U.S.-specific data include the race/ethnicity of students (from questions added to the U.S. version of the TIMSS student questionnaire) and the percentage of students in a school eligible for the federal free or reduced-price lunch program (from questions added to the U.S. version of the TIMSS school questionnaire).
The TIMSS 2019 U.S. national PUFs are considered add-on files because they do not contain international variables, such as plausible values, sampling variables, or weight variables; therefore, they must first be merged with the international U.S. data files before any analyses can be conducted. For TIMSS 2015 and prior cycles, U.S. national PUFs include international variables as well as the U.S.-specific variables that are not part of the U.S. international data files.
The U.S. national PUFs for each cycle, as well as the U.S. technical reports describing the content of the U.S. national PUFs in detail, are available from the National Center for Education Statistics (NCES) by download from the “Data Products” link on the TIMSS Publications and Products page. The national PUFs include student, school, and teacher data in ASCII text format; SPSS and SAS control files for reading the ASCII data to produce SPSS and SAS data files; codebooks; illustrative merging codes; a Read Me file; and a Quick Guide.
Note that there is no national public-use version of the TIMSS 1999 data files; only a national restricted-use version is available, which also includes the rescaled U.S. TIMSS 1995 data for those wishing to conduct analyses of the 1995 and 1999 datasets.
3. TIMSS U.S. national restricted-use data files (RUFs)
The U.S. national restricted-use data files (RUFs) can only be obtained by completing a restricted-use license agreement with NCES. Unlike the U.S. PUFs, the U.S. RUFs contain restricted-use variables, such as the NCESSCH (the NCES unique public school identification code) and PPIN (the private school unique identification number). These two variables allow users with restricted-use licenses to link TIMSS school ID numbers to the school ID numbers as they appear in the publicly available Common Core of Data (CCD) and Private School Universe Survey (PSS). Because these data can reveal the identities of participating schools, the restricted-use data files are only available to those who have obtained an NCES restricted-use data license. To learn about the licensing process, please visit https://nces.ed.gov/statprog/instruct.asp.
The content of the U.S. national RUFs is described under the “Data Products” link on the TIMSS Publications and Products page and further explained in the U.S. technical reports, which are also available from the TIMSS Publications and Products page.