The current issue of ESRI's ArcUser magazine has yet another article in a very good series by the ESRI chief demographer, Lynn Wombold. It's available online at: http://www.esri.com/news/arcuser/0708/demoarticle.html "Examining Error: Consider the Effect of Sample Size and Error Source when using census data." ArcUser magazine, spring 2008, pp. 8-11. Chuck Here's Elaine's link to the winter 2008 article: ************************************************************** Charles L. Purvis, AICP Principal Transportation Planner/Analyst Metropolitan Transportation Commission 101 Eighth Street Oakland, CA 94607-4700 (510) 817-5755 (office) (510) 817-7848 (fax) cpurvis(a)mtc.ca.gov (e-mail) www: http://www.mtc.ca.gov/ ************************************************************** For a nice article on ACS sampling, please see: http://www.esri.com/news/arcuser/0408/samplesize.html Sample Size Matters: Caveats for users of ACS tabulations by Lynn Wombold, ESRI Chief Demographer ArcUser Winter 2008 pps 9-11 Elaine Murakami FHWA Office of Planning 206-220-4460