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Unformatted text preview: Chapter 21 Notes Examples 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 = 100 is approximately normal with mean = p = 0.71 standard deviation = 045 . 100 2059 . 100 ) 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. • 67 out of 100 students are from SC. 67 . 100 67 ˆ = = p ) 76 . , 58 . ( 09 . 67 . ) 047 . ( 2 67 . 100 2211 . 2 67 . 100 ) 33 . )( 67 . ( 2 67 . ) 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 0.58 (58%) and at most 0.76 (76%). Example A bank randomly selected 250 checking account customers and found that 110 of them also had savings accounts at the same bank....
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 Spring '07
 JOHNSON
 Standard Deviation, true proportion, USC students

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