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Unformatted text preview: Confidence Intervals Definition . Level C confidence inter val (C.I.) for is interval ( L,U ) where L,U obtained from data, such that P ( L U ) = C no matter what . Typically, C = 0 . 90 , . 95 , . 99 . C.I. is interval estimator, represents set of plausible estimates for , unlike a point estimator which is only one value and doesnt take into account sampling error. 1 C.I. Normal Mean & Known Variance Let = population mean. Point es timator = X is unbiased. Sampling distribution is X when population is normal. 2 How to find C.I. Standardize: Z = Find from normal table value z * with P ( ) = C 3 Substitute P ( ) = C Rearrange inequalities 4 Hence C.I. has structure X = point estimate ME where margin of error ME = z * n 5 Suppose C = 0 . 90 , 1 C 2 = . 10 2 = 0 . 05 ,. Look up z * corresponding to 1 1 C 2 = 1 . 05 = 0 . 95 . Get z * = 1 . 645 ....
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This note was uploaded on 01/03/2012 for the course EE 1244 taught by Professor Drera during the Fall '10 term at Conestoga.
 Fall '10
 drera

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