Q: My copy of an earlier year of the NIS came with two 10% subsamples. What are these?
A: In the 2004 and earlier NIS, HCUP provided two 10% subsamples along with the core data file (a 20% sample) that would be used separately from each other. The 10% subsamples include their own discharges weights (DISCWT10), used to create national estimates for analysis.
These files were provided to allow analysts to test their models on a smaller set of data before running analysis on the full, weighted 20% sample. Because computer space and processing speed have grown so much, the subsamples are no longer provided.
Additional information is provided in the Introduction to the NIS, 2003 documentation available on the HCUP-US Website at http://www.hcup-us.ahrq.gov/db/nation/nis/nisarchive.jsp.