| Exam Board | CAIE |
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| Module | FP2 (Further Pure Mathematics 2) |
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| Year | 2009 |
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| Session | June |
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| Marks | 6 |
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| Topic | Hypothesis test of a normal distribution |
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6 The times taken by employees in a factory to complete a certain task have a normal distribution with mean \(\mu\) seconds and standard deviation \(\sigma\) seconds, both of which are unknown. Based on a random sample of 20 employees, the symmetric \(95 \%\) confidence interval for \(\mu\) is \(( 481,509 )\). Calculate a symmetric \(90 \%\) confidence interval for \(\mu\).
[0pt]
[6]