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Unformatted text preview: 1 Section 8.1 Estimate for large sample sizes The reliability of an estimate will be measured by the confidence interval estimates x error x =- Dont know Actually, we get an error tolerance x error - Let , means error E x E =- E x E - - x E x E - + ( ) , confidence interval x E x E- + In simplest terms, a 90 % confidence interval means that if you were to take many samples and find the interval each time, then 90% of those intervals will contain the population mean . Take 10 samples, find ten 90% confidence intervals, 9 out of the 10 should contain Area = 0.90 Area = 0.05 Area = 0.05 0.90 1.645 z = 0.90 1.645 z- = - 2 0.90 1.645 0.95 1.96 0.98 2.33 0.99 2.58 c c c c c z c z c z c z = = = = = = = = ZInterval Arrow to highlight Stats and press enter, Arrow down to enter , , ,and , x n C level - Arrow down to highlight Calculate and press enter....
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- Fall '07