05exS - ISOM111 Business Statistics (Fall 2010) Solutions...

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ISOM111 Business Statistics (Fall 2010) Solutions for Tutorial Exercise 5 1. Let X be the number of recovery days by new therapy and μ be its mean. (a) x =12 σ =3 n =70 As n =70 > 30 , by CLT, X N ( μ, σ 2 70 ) The 95% con f dence interval for the mean recovery days by new therapy is : x ± z 0 . 025 ( σ n )=12 ± 1 . 96( 3 70 )=(11 . 2972 , 12 . 7028) (b) x =12 σ =3 n =25 As we don’t know the distribution of X n =25 < 30 assume X N X N ( μ, σ 2 70 ) The 95% con f dence interval for the mean recovery days by new therapy is : x ± z 0 . 025 ( σ n )=12 ± 1 . 96( 3 25 )=(10 . 824 , 13 . 176) (c) B =0 . 5 B> n n> ( 2 . 576 3 0 . 5 ) 2 > 238 . 8879 Take z =2 . 576 ,n> 238 . 8879 n =239 Take z =2 . 575 ,n> 238 . 7025 n =239 Take z =2 . 58 ,n> 239 . 6304 n =240 (d) From part (b), B =1 . 176 B > n 1 . 176 > z 3 70 z 6 1 . 176 70 3 6 3 . 28 With z =3 . 28 ,con f dence level
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This note was uploaded on 01/06/2011 for the course ISOM 111 taught by Professor Hu,inchi during the Fall '10 term at HKUST.

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05exS - ISOM111 Business Statistics (Fall 2010) Solutions...

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