The IALS study defined literacy as "using printed and written information to function in society, to achieve one's goals, and to develop one's knowledge and potential" (NCES IALS Technical Report). IALS measured three domains of literacy:
The three domains each encompass a common set of skills relevant for diverse tasks. Scores were reported for each domain.
IALS adopted its methodology and scales from the 1992 U.S. National Adult Literacy Survey (NALS). The definition of literacy used in IALS was developed and refined from that used in the 1992 NALS. IALS also adopted a number of items from NALS in order to make the assessments comparable. On the prose and document scales, 50 items from NALS were used in IALS. On the quantitative scale, 26 items were carried over, for a total of 76 NALS items in IALS. For more information on NALS, visit the collection of NALS publications on the NAAL website.