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Unformatted text preview: 9 . 25 = x and a standard deviation 7 . 2 = s . a. Find a 95% confidence interval for the population mean . b. Find a 90% confidence interval for . c. Find a 99% confidence interval for . 4. Periodically, the Hillsborough County (Florida) Water Department tests the drinking water of homeowners for contaminants such as lead and copper. The lead and copper levels in water specimens collected for a sample of 10 residents of the Crystal Lakes Manors subdivision are shown in the next table. Lead (g/L) Copper (mg/L) 1.32 .508 .279 13.1 .320 .919 .904 .657 .221 3.0 .283 1.32 .475 4.09 .130 4.45 .220 .743 1 a. Construct an 99% confidence interval for the mean lead level in water specimens from Crystal Lakes Manors. b. Construct an 99% confidence interval for the mean copper level in water specimens from Crystal Lakes Manors. 2...
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- Spring '11