This section describes the methodology used to prepare estimates of adult literacy proficiencies for Iowa community college districts.

It is assumed that readers of this section are familiar with survey-based and synthetic estimates prepared on a national scale for most U.S. counties and larger places (cities). For more information on these estimates refer to main adult literacy proficiencies page on this Internet site.

There are 15 Iowa community college districts. A map of these districts may be viewed on the Iowa adult literacy proficiencies maps and charts page. Community college districts are comprised of whole school districts which, in many cases, span county boundaries. To prepare community college district estimates, a methodology was developed to estimate the number of persons 16 years and over at NALS Level 1, NALS Level 2 and Level 1 plus Level 2 by segment of school district contained in its respective county. Estimates were prepared for 866 school district segments and then aggregated into community college districts.

The first step in the process was to associate the 115,860 1990 census blocks with the school district in which they are located. This step is necessary because school districts that split across county lines are broken into units of census blocks and split census blocks. A census block is a statistical geographic area which is the smallest unit of geography for which data are tabulated from any statistical program but most notably the decennial census.

Only by knowing the population in these blocks and split blocks is it possible to determine how much of a school district's population is contained in the county in which it is located. (While it is possible to determine the geographic proportion of that part of the school district contained in the county, this proportion is considered less valuable for the present estimation purposes since large areas of some school districts may be very sparsely very densely inhabited -- using geographic proportions alone would result in less accurate estimates than the methodology used here.)

It is possible to determine the population of split census blocks through the use of a cross reference file developed from the 1990 census mapping project sponsored by the U.S. Department of Education which was the first national scale program to map all public school districts.

In summary, the total population for split or whole census blocks were associated with the every community college district by the county and the school district in which it is located. The total population was then determined for each part school district contained in each county.

County level synthetic estimates were then allocated to school district parts for each of three categories: NALS Level 1, NALS Level 2, and NALS Level 1 + Level 2. The school district segment estimates were then aggregated to determine the cumulative number of persons 16 and over at Level 1, Level 2, and Level 1 + Level 2. These cumulative numbers were then divided by the total persons 16 and over in each community college district to determine the proportion of persons 16 and over at NALS Level 1, NALS Level 2, and NALS Level 1 + Level 2 by community college district.

Links to other adult literacy proficiencies pages on this site:
    •   Adult Literacy Proficiency main page
    •   Iowa Adult Literacy Proficiency Profiles and Tables