Where to draw the line? Probably comes down to what's your tolerance for error in informing decisions you want to make... Earlier in my career, I worked in a State labor market research shop. In survey work for US BLS, we would only publish survey-based stats where relative standard error (std error as % of the central estimate) was less than 30% (for average wage) or less than 50% (for employment levels). The wage statistics had a more stringent standard than employment levels because of the nature of the data (there was less variation and uncertainty around wages) and because of perceived criticality (data user audiences expected and needed greater accuracy). Hope that helps. --Todd Graham Metropolitan Council Research From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces(a)chrispy.net] On Behalf Of Mara Kaminowitz Sent: Wednesday, December 22, 2010 10:11 AM To: ctpp-news(a)chrispy.net Subject: RE: [CTPP] ACS 2005-09 data What I would like to know is how much MOE is too much to be useful? I have been looking at the census tract MOE's for certain variables in my region and they range from 25% to 200%. It's not pretty. And that's not even the obscure sub-categories. Where do other people draw the line when determining data reliability? Mara Mara Kaminowitz GIS Analyst ......................................................................... Baltimore Metropolitan Council Offices at McHenry Row 1500 Whetstone Way Suite 300 Baltimore, MD 21230 410-732-0500 ext. 1030 mkaminowitz(a)baltometro.org<mailto:mkaminowitz(a)baltometro.org> www.baltometro.org <http://www.baltometro.org>

Thank you for the information, it helped greatly. I had one further question. How do you handle the Margin of Errors(MOE) for median, mean and rate values of combine areas? For example the MOE for the "median family income" or "rental vacancy rate" for combine areas like counties. Is it the same process as the estimates MOE calculations referred to http://www.census.gov/acs/www/Downloads/handbooks/ACSResearch.pdf in Appendix 3 on page A-14 under section "Calculating MOEs for Aggregated Count Data" or is there a different formula to calculate it? I am trying to develop a regional profile of 12 combined counties in south central Ohio. I was able to calculate the estimates and their MOEs based off the guide that is mentioned in the link, but I am having trouble with the estimates for rates, means, and medians in getting their combined MOE. Thanks Jason From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces(a)chrispy.net] On Behalf Of Graham, Todd Sent: Wednesday, December 22, 2010 10:27 AM To: ctpp-news(a)chrispy.net Subject: RE: [CTPP] ACS 2005-09 data It's all basic statistics. Our State Demographer's Office took the Census-provided documentation for error calculation and built a general, multi-purpose spreadsheet. It's ready to use, and a big time saver.... Statistical Significance Calculator (excel file): www.demography.state.mn.us/documents/StatisticalCalculationsMenu.xls<htt… All you need to do is plug in the "n", etc., and you'll have what you need. ________________________ Todd Graham Principal Forecaster Metropolitan Council 390 Robert Street North Saint Paul, MN 55101 ph: 651/602-1322 email: todd.graham(a)metc.state.mn.us<mailto:todd.graham(a)metc.state.mn.us> in: www.linkedin.com/in/toddgraham web: http://stats.metc.state.mn.us/ ________________________ From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces(a)chrispy.net] On Behalf Of Krishnan Viswanathan Sent: Wednesday, December 22, 2010 8:23 AM To: ctpp-news(a)chrispy.net Subject: Re: [CTPP] ACS 2005-09 data Look here for details: http://www.census.gov/acs/www/guidance_for_data_users/handbooks/ and the document what Researchers need to know will help you too: http://www.census.gov/acs/www/Downloads/handbooks/ACSResearch.pdf On Tue, Dec 21, 2010 at 10:22 AM, Jason Gillow <jason.gillow(a)ovrdc.org<mailto:jason.gillow(a)ovrdc.org>> wrote: Hello I was wondering how do you handle combining different geographic areas with each other to form a regional profile. For example, my office is a regional planning organization that serves 12 counties. I want to take the profile data from ACS 2005-09 5-year estimates for each county and form a profile of my regional, I know how to combine the estimates and do the percentages, but how do I handle the margin of error columns? Is there their a reference or guidance on this? Thank you Jason Jason Gillow Research/Planning Specialist II Ohio Valley Regional Development Commission 9329 St Rt 220 E, Suite A Waverly, OH 45690 Phone: 740-947-2853 or 800-223-7491 (In Ohio) Fax: 740-947-3468 www.ovrdc.org<http://www.ovrdc.org> Email: jgillow(a)ovrdc.org<mailto:jgillow(a)ovrdc.org> _______________________________________________ ctpp-news mailing list ctpp-news(a)chrispy.net<mailto:ctpp-news(a)chrispy.net> http://www.chrispy.net/mailman/listinfo/ctpp-news -- Krishnan Viswanathan 1101 High Meadow Dr Tallahassee FL 32311