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NAEP Technical DocumentationEstimated Grade Enrollment and Measure of Size for the 2000 State Assessment

A school's estimated grade enrollment approximates the number of students enrolled in the assessed grade (either fourth or eighth grade). The measure of size standardizes a school's estimated grade enrollment for calculating the school sampling probability.

Dividing a school's total student enrollment by its number of grades results in its estimated grade enrollment. Schools with missing total student enrollment values receive estimated grade enrollments equal to 20 students. The value 20 was chosen because it leads to a measure of size that yields a self- weighting sample of students within the school.

A school's measure of size depends on its estimated grade enrollment. The purpose of this measure is twofold. First, selecting schools with probability proportional to size (PPS) sampling reduces the variances in NAEP. Second, sampling very small schools less frequently than their size would dictate reduces the cost per student of data collection.

The table below provides the formula to calculate a school's measure of size.

Calculation of a school's measure of size, state assessment: 2000

Estimated grade enrollment (EGE)	Measure of size
EGE < 10	30
10 = EGE < 20	3 x EGE
20 = EGE < 65	60
EGE = 65	EGE
EGE unknown	60
SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2000.

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