Survey Design and Sample Sizes
Key features of the ELS:2002 design are listed below, along with base year (2002) sample sizes:
Base Year (2002)—Data Released in April 2004
- Baseline survey of high school sophomores, in spring term, 2002.
- Cognitive tests administered in reading and mathematics.
- Questionnaires administered to parents, math and English teachers, school principals, and heads of the school library media center.
- Sample sizes:
- 750 schools (questionnaires: principals, head librarians or media center directors; facilities checklists completed by survey administrators).
- Over 15,000 students and their parents.
- Mathematics and English teachers—one each for each student.
- Schools selected first, then tenth-grade students selected randomly within each school.
- Non-public schools (specifically, Catholic and other private schools) sampled at a higher rate, ensuring that sample is large enough to support comparisons with public schools.
- Asian students sampled at a higher rate than White, Black, and Hispanic students, ensuring that the sample is large enough to support comparisons with those groups.
First Follow-up (2004)—Data Released in December 2005
- First follow-up survey occurred in 2004, when most sample members were high school seniors,
but others were in others grades; also some were dropouts and some completed high school early.
- Questionnaires administered to all students still in school, early completers, dropouts, and school administrators.
- Cognitive test administered in mathematics.
- Students from the Base Year sample:
- Those still in the 750 schools included in the Base Year sample (12,400).
- Those in the Base Year sample who had transferred to a different school (1,100).
- Early completers and dropouts (1,300).
- ELS:2002 began with a representative sample of high school sophomores. For ELS:2002 to also contain a fully representative sample of high school seniors two years later, the base year cohort was "freshened." What freshening means is that spring term 2004 seniors who were not sophomores in the U.S. in spring term of 2002 (for example, students who were out of country, or in another grade sequence because of skipping or failing a grade) were given a chance of selection into the survey.
- Thus, the First Follow-up sample both continues the longitudinal sample of spring 2002 sophomores and represents all the nation's spring term 2004 high school seniors.
First Follow-up Transcript Study—Data Released in December 2006
- High school transcripts were collected for all students from their base year school and, if they had changed schools, also their transfer schools. These transcripts provide school archival records on courses completed, grades, attendance, SAT/ACT scores, and so on from grades 9 through 12.
Second Follow-up (2006)—Data Released in October 2007
- The Second Follow-up occurred in 2006, when many sample members were in college for up to their second year of enrollment, while others were employed and may not have ever attended college. Some who had previously dropped out of high school may have earned a General Education Development (GED) or other equivalency certificate or be working on a GED.
- All sample members who were respondents in the Base Year and/or the First Follow-up were included.
- Survey information was obtained from sample members by a web-based self-administered interview; computer-assisted telephone interview; or computer-assisted personal interview.
One additional follow-up will be conducted in 2012, which 6 years after the Second Follow-up or 8 years after high school graduation. Retrospective data on the college enrollment and employment histories of sample members will be collected, along with information about their marital status, families, and participation in the community. College transcripts showing all courses completed for each college attended and possibly student financial aid data for all years of college from all sources will also be obtained.