Data Files

The U.S. ICILS data are available in separate files, and depending on the analysis needs, different data files may need to be merged to have the complete data.

• Student achievement data—as well as student, teacher, school, and ICT coordinator survey data for international variables—are available in the U.S. data files in the ICILS International Database
• U.S.-specific survey variables are available in two formats: the U.S. national public-use data files and the U.S. national restricted-use data files.

The differences between these data files are summarized in the following table and described in detail below it.

It should also be noted that the ICILS data are complex due to the study’s multi-stage sample design and use of imputed scores (also known as plausible values). To help users explore ICILS data, we have compiled a list of NCES online tools and tutorials on ICILS. Please visit our Analyzing Tools page for details.

Table 1: Comparing three versions of U.S. ICILS data

Version	U.S. data for international variables	Other participating education systems’ data for international variables	U.S.-specific variables (e.g., race/ethnicity, poverty)	U.S.-specific restricted-use data (e.g., CCD ID)
1. ICILS International U.S. data files	Yes	Yes	No	No
2. ICILS U.S. national public-use data files	No	No	Yes	No
3. ICILS U.S. national restricted-use data files	No	No	No	Yes

1. ICILS International Data Repository

The ICILS International Data Repository is released for each round of ICILS. It consists of data files containing the set of international variables that are common to all participating education systems, including the United States. The ICILS International Data Repository, its user’s guide (describing the organization and content of the database) and supplements, and supporting materials (including the SAS/SPSS control files, international codebooks and data almanacs, international background questionnaires, and released items) are available for download from the IEA’s Data Repository website. IEA’s website also lists publications that may be of use to data users (e.g., ICILS technical reports, international data reports, and assessment frameworks).

2. ICILS U.S. national public-use data files

In addition to the information collected through the international variables, each country has the option to collect additional nationally specific information as part of the international questionnaires. In each round of ICILS, the United States has used this option to collect some U.S.-specific information that is not included in the ICILS International Database. For example, the additional U.S.-specific information includes the race/ethnicity of students (from questions added to the U.S. version of the ICILS student questionnaire) and the percentage of students in a school eligible for the federal free and reduced-price lunch program (from questions added to the U.S. version of the ICILS school questionnaire). Categorical variables are created based on the responses to the U.S.-specific questions. These variables are available in the ICILS U.S. public-use data files, which can be downloaded from the ICILS Data Products.

3. ICILS U.S. national restricted-use data files

The ICILS U.S. national restricted-use data files include sampling variables and original continuous variables that are used to create the categorical variables included in the public-use files. Sampling variables, such as the NCES school ID allow ICILS data to be linked to other NCES data files. The continuous variables will allow analysis of smaller subcategories. The restricted-use data files are only available to those who have obtained an NCES restricted-use data license. Directions on how to obtain the license can be found at http://nces.ed.gov/pubsearch/licenses.asp.