The school response rates for the 2008 NAEP long-term trend (LTT) assessment include response rates for public and private school samples for age groups 9, 13, and 17 in the reading and mathematics assessments. Both subjects have the same school response rates because virtually all the sample schools assessed both subjects and the school nonresponse weighting adjustment was computed and applied at the school level.
The student response and exclusion rates for the 2008 NAEP LTT assessment include the overall weighted student response rates and exclusion rates for the reading and mathematics assessments for public and private school students in age groups 9, 13, and 17. Excluded students were identified as they were in the 2007 grade 4, 8 and 12 assessments.
NCES statistical standards call for a nonresponse bias analysis to be conducted for a sample with a response rate below 85 percent (the base weighted response weight).