NAEP Assessment Sample Design → NAEP 2008 Sample Design → 2008 Long-Term Trend (LTT) Assessment Sample Design → Age Distribution Fractions

NAEP Technical DocumentationAge Distribution Fractions

			Age Distribution Fractions for Ages 9 and 13 Age Distribution Fractions for Age 17

Age distribution fractions are estimated proportions of students in each grade that are age-eligible. The fractions are components in the school measure of size. The computation of the age distribution fractions was done differently by age group. For ages 9 and 13, a breakout by every birth-year cohort represented in the relevant grades was fully carried out. The approach was simpler for the age 17 sample, using an age range between 16- and 17-years-old, because this age definition is based on an October-September birth cohort.

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