National Assessment of Adult Literacy, 2003

The NAAL household samples (including the national sample and the six SAAL samples) were selected on the basis of a four-stage, stratified area sample: (1) primary sampling units (PSUs) consisting of counties or groups of contiguous counties; (2) secondary sampling units (referred to as segments) consisting of area blocks; (3) housing units containing households; and (4) eligible persons within households. Person-level data were collected through a screener, a background questionnaire, the NAAL literacy assessment, and the oral module. The NAAL household sample contains 160 PSUs, 2,818 segments, 35,365 housing units, and 23,732 persons. Sampling frame: For the initial stage of sampling, a PSU frame was created by using the census 2000 public law (PL)-94 county–level files. The PSUs were formed by combining adjacent counties, respecting their population sizes and taking into consideration the travel distance for interviewers. The PSUs were formed as a single county or a group of contiguous counties, depending on the population size and the end-to-end distance within a PSU. For the second stage of sampling, a frame of segments was created within the selected PSUs by using the census 2000 summary file (SF) block data. After segments were selected, the data collection contractor’s listers visited each sampled segment to create a sampling frame of housing units for the third stage of sampling. At the fourth stage of sampling, a complete list of household members was obtained by interviewers and entered in the CAPI program. Before sample selection, the CAPI system determined the eligibility of each person listed.

The NAAL prison sample was selected in two stages: (1) the selection of primary sampling units (PSUs) made up of federal and state prisons and (2) the selection of inmates within each selected facility. At the first stage prisons were selected with probabilities proportional to the number of inmates in the facility. At the second sampling stage, an average of about 12 inmates were selected from the participating sampled facilities. Approximately 1,200 inmates were selected from 107 prisons. Sampling frame: The Prison Census list of facilities was compared with the ACA directory list to arrive at a sampling frame of prisons eligible for the study. Inmates in each prison were selected from a list of inmates occupying a bed the previous night.

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