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NAEP Technical DocumentationStratification by Urbanization Classification for the 2011 State Assessment

The creation of the urbanicity classification variable was based on the NCES urban-centric locale and was defined within each explicit stratum. The NCES urban-centric locale contains the following categories:

1. Large City: Territory inside an urbanized area and inside a principal city with population of 250,000 or 
     more.

2. Mid-size City: Territory inside an urbanized area and inside a principal city with population less than 
     250,000 and greater than or equal to 100,000.

3. Small City: Territory inside an urbanized area and inside a principal city with population less than
     100,000.

4. Large Suburb: Territory outside a principal city and inside an urbanized area with population of 250,000 or
     more.

5. Mid-size Suburb: Territory outside a principal city and inside an urbanized area with population less than
     250,000 and greater than or equal to 100,000.

6. Small Suburb: Territory outside a principal city and inside an urbanized area with population less than
     100,000.

7. Fringe Town: Territory inside an urban cluster that is less than or equal to 10 miles from an urbanized
     area.

8. Distant Town: Territory inside an urban cluster that is more than 10 miles and less than or equal to 35
     miles from an urbanized area.

9. Remote Town: Territory inside an urban cluster that is more than 35 miles of an urbanized area.

10. Fringe Rural: Census-defined rural territory that is less than or equal to 5 miles from an urbanized area,
     as well as rural territory that is less than or equal to 2.5 miles from an urban cluster.

11. Distant Rural: Census-defined rural territory that is more than 5 miles but less than or equal to 25 miles
     from an urbanized area, as well as rural territory that is more than 2.5 miles but less than or equal to 10
     miles from an urban cluster.

12. Remote Rural: Census-defined rural territory that is more than 25 miles from an urbanized area and is
     also more than 10 miles from an urban cluster.

13. Outside of the United States: Department of Defense Education Activity (DoDEA) overseas schools.

For the definitions of the geographic terms used in these descriptions, please refer to the Census Bureau’s website (for example, www.census.gov/geo/www/ua/ua_2k.html; www.census.gov/population/www/metroareas/aboutmetro.html)

The urbanicity classification cells were created by starting with the original NCES urban-centric locale categories. Urbanicity strata were collapsed with neighboring strata until a minimum cell size criterion, in terms of the percentage of students, was met. The minimum cell size criterion varied by type of explicit stratum. The criterion for explicit strata comprising the largest TUDA districts (Los Angeles, New York City, Chicago, Miami, and Houston) was 12 percent; for the other TUDA districts, it was 18 percent; and for all other explicit strata, it was 9 percent.

The urbanicity classification variable was equal to the original NCES urban-centric locale if no collapsing was necessary. If collapsing was necessary, the collapsing scheme first collapsed within the four major strata (city, suburbs, town, rural), in this order. For example, urbanicity categories 1, 2, and 3 within City were collapsed in order of the list (1 with 2, 2 with 3) if cells 1 or 3 were deficient. If the middle cell (e.g., 2) was deficient, then it was collapsed with the smaller of the two end cells. If a collapsed pair was still deficient, it was collapsed with the remaining unit within the major stratum. That is, a single category would be created by combining large city, mid-size city and small city categories. If these collapsed cells were still inadequate, they were further collapsed with all three types of suburb cells to form a single cell made up of large, mid-size and small cities and large, mid-size and small suburbs. The values of the urbanicity classification variable were set equal to the cell value of the final level of collapsing.

Prior experience with this type of stratification has shown that the greatest efficiency of stratification results when cities and suburb fringe areas are always kept separate from towns and rural areas, even if the enrollment criterion is violated.

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