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petitioned the U.S. Supreme Court to grant ... - Election Law Blog

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36aAppendix Dwith sampling error actually makes <strong>the</strong> data more reliable,because <strong>the</strong> margin of error serves as a measure thatcan be applied <strong>to</strong> judge its statistical accuracy relative <strong>to</strong>o<strong>the</strong>r data sources. For <strong>the</strong> reasons enumerated by Mr.Ely as well as <strong>the</strong> Census Bureau’s reliance on ACS data(as discussed infra, section III.B.2.d), <strong>the</strong> <strong>Court</strong> finds thatACS data is accurate and reliable.b. Discrepancy in 2006 and 2007 ACS FiguresDr. Rives also explained that <strong>the</strong> numbers providedin <strong>the</strong> ACS are “point estimates,” which is <strong>the</strong> best singlevalue provided by <strong>the</strong> Census Bureau for <strong>the</strong> characteristicin question (here, HCVAP). Every point estimate issubject <strong>to</strong> a margin of error that is always published by<strong>the</strong> Census Bureau along with <strong>the</strong> point estimate. (TrialTr. vol. 1, 78, Feb. 18.) Adding and subtracting <strong>the</strong> marginof error from <strong>the</strong> point estimate provides a range. Thatrange falls within a 90% confidence interval, i.e., <strong>the</strong>reis a 90% chance that <strong>the</strong> range surrounding <strong>the</strong> pointestimate contains <strong>the</strong> truly accurate value. (Id.) The 2006ACS lists <strong>the</strong> Hispanic population in Irving as 85,960and <strong>the</strong> margin of error is 10,595. Thus, <strong>the</strong>re is a 90%chance that <strong>the</strong> actual Hispanic population in Irving fallssomewhere between 96,555 and 75,365. In 2007, <strong>the</strong> ACSpoint estimate for Irving’s Hispanic population was 75,084with a margin of error of 8,120. Comparing 2006 ACS data<strong>to</strong> 2007 ACS data, Dr. Rives argued, demonstrates thatgrowth rates derived from ACS data should not be reliedupon. Dr. Rives suggested that <strong>the</strong> 11,000 person changein <strong>the</strong> point estimate between 2006 and 2007 reflectssignificant sampling error in combination with a declinein <strong>the</strong> Hispanic population in Irving. (Id. at 79-80.)

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