Below is a simplified description of the 2003 National Assessment of Adult Literacy

(NAAL), which is a nationally representative assessment of English literacy among American

adults age 16 and older. Over 19,000 adults participated, representing the entire population of

U.S. adults who are age 16 and older. (A series of questions follow the sample description.)

Sample Design Description:

A sample design was employed that first required the selection of counties from across the

nation. There are 3,140 counties in the U.S. From the 3,140 counties, about 2,000 geographic

areas were formed by grouping contiguous counties together with the objective of reaching a

minimum size.After the 2000 geographic areas were formed, they were grouped into 100 strata, based on census division, race/ethnicity distribution, per capita income, and Metropolitan Statistical Area status (i.e., urbanicity). From each stratum, one geographic area was selected, resulting in 100 counties (or groups of counties) in the sample. Within each of the 100 strata, the larger the geographic area (comprising of single or multiple counties), the higher the probability of inclusion in the sample. Within each selected PSU, area segments (census blocks or groups of blocks) were selected with a probability proportional to the number of housing units they contained. However, area segments that were classified as high-minority (more than 25 percent Black or Hispanic) were oversampled. Field staff visited all selected area segments and prepared a list of housing units located within those segments using block maps from the 2000 Census. From this list, households were systematically selected within each segment. Minority households in high-minority segments were given a higher chance of being selected.a.

Question:Describe the complex sample features utilized in this sample design. Include the number of stages of selection and the sampling unit at each stage. Describe stratification and or unequal/equal selection at each stage.

Hint:Explain the sample design that is provided in the example, including what they are doing at each sampling stage in terms of stratification and whether there is clustering and unequal selection at that stage. There are 4 stages of selection, meaning different units are selected at each of these four stages. These units should be described along with the unequal selection and/or stratification and/or clustering at each stage.