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Unformatted text preview: Chapter 21 Notes Examples Page 1 of 3 Example: USC Students From South Carolina • Suppose the true proportion of USC students from SC is 0.71 (71%). • Then, the sampling distribution of p ˆ for n = 137 is approximately normal with mean = p = 0.71 standard deviation = 039 . 137 2059 . 137 ) 29 . )( 71 . ( ) 1 ( = = = − n p p Example: USC Students From South Carolina • Compute and interpret a 95% confidence interval for the true proportion of USC students who are from SC. Let’s say that this class is our sample. 79 out of 137 students are from SC. 58 . 137 79 ˆ = = p ) 66 . , 50 . ( 08 . 58 . ) 042 . ( 2 58 . 137 2436 . 2 58 . 137 ) 42 . )( 58 . ( 2 58 . ) ˆ 1 ( ˆ 2 ˆ = ± = ± = ± = ± = − ± n p p p We are 95% confident that the true proportion of USC students who are from SC is at least 0.50 (50%) and at most 0.66 (66%). Example A bank randomly selected 250 checking account customers and found that 110 of them also had savings accounts at the same bank. Calculate the sample proportion of checking account customers who also have savings accounts....
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 Fall '07
 JOHNSON
 Statistics, Standard Deviation, true proportion

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