NAEP Assessment Sample Design → NAEP 2008 Sample Design → Selection of Primary Sampling Units (PSUs) for the 2008 Assessment → Primary Sampling Unit (PSU) Frame: Stratification for the 2008 Assessment → Final Primary Sampling Unit (PSU) Strata for the 2008 Assessment

Final Primary Sampling Unit (PSU) Strata for the 2008 Assessment

The strata were defined using the selected stratifiers from the stepwise regression analysis (see Stepwise Regression Analysis Results for PSU Stratification). The cutoffs were selected so that roughly equal measures of size were represented by each stratum.

NAEP Technical DocumentationStratification for Northeast metropolitan noncertainty primary sampling units (PSUs), by stratum: 2008

Stratum	Primary stratifier	Secondary stratifier	PSUs	Measure of size
† Not applicable. NOTE: Measures of size are rounded to the nearest thousand. Numbers may not sum to total due to rounding. Black includes African American. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2008.
Total	†	†	46	4,687,000
1	Percent child poverty <=10.1%	Percent Black <=15.9%	8	581,000
2	Percent child poverty <=10.1%	15.9%< Percent Black <=27.7%	2	558,000
3	10.1%< Percent child poverty <=12.5%	Percent Black <=14.9%	7	589,000
4	10.1%< Percent child poverty <=12.5%	14.9%< Percent Black <=38.2%	4	632,000
5	12.5%< Percent child poverty <=13.4%	†	5	556,000
6	13.4%< Percent child poverty <=15.1%	†	7	601,000
7	15.1%< Percent child poverty <=17.0%	†	5	549,000
8	17.0%< Percent child poverty <=20.7%	†	8	622,000
Mean	†	†	†	586,000

Stratification for Northeast non-metropolitan noncertainty primary sampling units (PSUs), by stratum: 2008

Stratum	Primary stratifier	PSUs	Measure of size
† Not applicable. NOTE: Measures of size are rounded to the nearest thousand. Numbers may not sum to total due to rounding. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2008.
Total	†	50	1,150,000
1	Percent child poverty <=15.7%	23	587,000
2	15.7%< Percent child poverty <=22.8%	27	563,000
Mean	†	†	575,000

Stratification for Midwest metropolitan noncertainty primary sampling units (PSUs), by stratum: 2008

Stratum	Primary stratifier	Secondary stratifier	Tertiary stratifier	PSUs	Measure of size
Total	†	†	†	100	7,328,000
1	Child poverty <=12.5%	†	Pct Asian <=1.1%	17	620,000
2	Child poverty <=12.5%	†	1.1%< Pct Asian <=1.4%	4	646,000
3	Child poverty <=12.5%	†	1.4%< Pct Asian <=2.4%	8	576,000
4	Child poverty <=12.5%	†	2.4%< Pct Asian <=2.6%	3	668,000
5	Child poverty <=12.5%	†	2.6%< Pct Asian <=3.4%	7	578,000
6	Child poverty <=12.5%	†	3.4%< Pct Asian <=10.3%	13	588,000
7	12.5%< Child poverty <=12.9%	†	†	6	603,000
8	12.9%< Child poverty <=14.5%	†	Pct Asian <=1.3%	7	617,000
9	12.9%< Child poverty <=14.5%	†	1.3%< Pct Asian <=2.7%	7	608,000
10	14.5%< Child poverty <=27.6%	Med Income <=$38,291	†	17	608,000
11	14.5%< Child poverty <=27.6%	$38,291< Med Income <=$46,460	Pct Asian <=0.9%	7	592,000
12	14.5%< Child poverty <=27.6%	$38,291< Med Income <=$46,460	0.9%< Pct Asian <=3.1%	4	623,000
Mean	†	†	†	†	611,000

Stratification for West non-metropolitan noncertainty primary sampling units (PSUs), by stratum: 2008

Stratum	Primary stratifier	Secondary stratifier	Tertiary stratifier	PSUs	Measure of Size
† Not applicable. NOTE: Measures of size are rounded to the nearest thousand. Numbers may not sum to total due to rounding. Percent HS graduates = percent high school graduates. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2008.
Total	†	†	†	102	1,689,000
1	Percent college graduates <=21.0%	Median child poverty <=17.3%	†	26	423,000
2	Percent college graduates <=21.0%	17.3%< Median child poverty <=43.0%	Percent HS graduates <=77.3%	23	421,000
3	Percent college graduates <=21.0%	17.3%< Median child poverty <=43.0%	77.3%< Percent HS graduates <=86.4%	28	420,000
4	21.0%< Percent college graduates <=42.6%	†	†	25	426,000
Mean	†	†	†	†	422,000

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