Re: [CTPP] aggregated MOE for 6 counties

Hi Mara, Each item that you aggregate will introduce some level of uncertainty since the exact distribution of aggregated data is not available to you. We can only estimate the aggregated MOE assuming that each item has similar statistical distributions. Since MOE is a function of variance, depending on how much variance there is in your data, aggregation may produce a confidence interval which can be reasonable or too large to be useful. You need to evaluate the reasonableness of the aggregated MOE estimates and associated confidence intervals. One possible way to start is to aggregate a smaller number of counties (two or three), add a new one each time, and track the changes in the MOE estimate. The following reference has information on how to work with MOEs. I also added a couple of other links I find useful. http://www.census.gov/acs/www/Downloads/handbooks/ACSGeneralHandbook.pdf http://www.census.gov/acs/www/guidance_for_data_users/handbooks/ http://www.census.gov/acs/www/methodology/methodology_main/ Hope this helps. Best of luck. Cemal. Cemal Ayvalik, PhD. Cambridge Systematics, Inc. 115 South LaSalle Street, Suite 2200 Chicago, IL 60603 tel : 312 665 0209 fax: 312 346 9908 e-mail: cayvalik(a)camsys.com www.camsys.com From: <mkaminowitz(a)baltometro.org> To: <ctpp-news(a)chrispy.net> Date: 03/15/2012 11:42 AM Subject: [CTPP] aggregated MOE for 6 counties Sent by: ctpp-news-bounces(a)chrispy.net Hello, I need to get a regional estimate and MOE composed of 6 counties. I know the rule of thumb is that aggregating MOE's doesn't work well for more than 4 units. Does anyone know is using 6 would cause the MOE to be inaccurate? 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 www.baltometro.org Confidentiality Statement This message may contain legally privileged and confidential information that is intended only for the use of the recipient(s) named above. If you are not an intended recipient, taking any action based on the contents of this message is strictly prohibited. Please immediately notify the sender if you have received this message in error. _______________________________________________ ctpp-news mailing list ctpp-news(a)ryoko.chrispy.net http://ryoko.chrispy.net/mailman/listinfo/ctpp-news