How can variances be calculated for NAMCS and NHAMCS estimates?
A. Prior to calendar year 2002, NAMCS and NHAMCS public use files did not contain the sample design variables that are needed by sophisticated computer software like SUDAAN, which computes standard errors while taking the complex multi-stage sampling design into account. The design variables are confidential and have never been released to the general public. However, in 2002, a 5-year research project culminated in a plan to mask sample design variables so that they could be released without fear of disclosure of survey participants. The 2000 public use files were released with these variables, and files from 1993-1999 were re-released to include them. We are currently working to add masked sample design variables to NAMCS files from 1989-1992, and to NHAMCS files. Please see the survey documentation for more information about using computer software like SUDAAN to calculate standard errors. Another method for calculating variances for NAMCS and NHAMCS estimates which does not require
