NAEP Analysis and Scaling → Scale Linking and Transformation to the Reporting Metric → Comparisons of Distributions of Linking Samples for NAEP Assessments → Comparison of Means and Percentiles of Original 2004 Scores and 2004 Transformed Provisional Scores, Age 9 Mathematics Long-Term Trend Assessment: 2008

Original estimates are based on previous assessment data and previous assessment scaling results, transformed to the reporting metric using the transformation identified during the analysis of the previous assessment data. Provisional estimates are based on previous assessment data and current assessment scaling results. These are on the theta metric specified by the scaling program. The original and provisional estimates for the linking sample are used to find the transformation constants necessary to place the current assessment scale scores on the scale used to report previous assessment scale scores. The transformed provisional estimates are based on previous assessment data and current assessment scaling results, transformed to the reporting metric using the transformation constants calculated from the original and provisional estimates for the linking sample. If the transformation constants are correct, the original and transformed provisional means should be the same.

NAEP Technical DocumentationComparison of means and percentiles of original 2004 scores and 2004 transformed provisional scores, age 9 mathematics long-term trend assessment: 2008

Scale	Statistic	Original 2004 estimate	2004 transformed provisional estimate	Difference between the provisional estimate and the original estimate
# Rounds to zero. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2008 Mathematics Long-Term Trend Assessment.
Composite scale	Mean	239.35	239.35	#
	10th percentile	193.06	192.86	-0.20
	25th percentile	218.45	218.44	-0.01
	50th percentile	242.61	242.74	0.13
	75th percentile	263.21	263.29	0.08
	90th percentile	280.27	280.29	0.02

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