IALS consisted of two components: a background questionnaire, about 20 minutes in length, and an assessment, which was not timed. The assessment consisted of about 45 assessment items (see Sample Items). Trained interviewers administered both components to participants in their homes. Participants were selected from a nationally representative sample and in some countries and regions they received a monetary incentive for participating1. Respondents were first asked to complete the background questionnaire, which was designed to collect general demographic information about participants (such as sex, age, race/ethnicity) as well as more targeted information related to their educational experiences, labor market experiences, and literacy related activities.
Once the background questionnaire was completed, the interviewer presented a booklet containing six simple tasks ("Core tasks"). If a respondent could not complete two of these tasks correctly, the interview was adjourned. Respondents who completed two or more of these tasks correctly were given a booklet with a larger variety of tasks drawn from a pool of 114 items grouped into blocks. They were encouraged to attempt each task, but there was no time limit and the survey was voluntary.
To reduce respondents' time burden without sacrificing good representation of the content domain, each respondent was administered only a fraction of the pool of tasks through a procedure known as matrix sampling. Each booklet was designed to take about 45 minutes to complete and contained three blocks that represented about 45 items. Overall, the assessment drew from seven blocks, each requiring approximately the same amount of response time and covering all three literacy domains (prose, document, and quantitative). IALS data were collected by participating countries in successive cycles of data collection between 1994 and 1998, using nationally representative samples of the adult population aged 16-65. In the United States, a nationally representative sample of 3,053 adults aged 16–65 participated in IALS. The U.S. data collection took place in October and November 1994.
For more information on the administration go to the NCES IALS Technical Report.
1 Two countries provided incentives: Germany gave away lottery tickets and Sweden gave a small reward. The United States did not offer any incentive in IALS. Source: https://nces.ed.gov/pubsearch/pubsinfo.asp?pubid=98053, page 94.