Stats 309 10-3

Stats 309 10-3 - Section 10.3 We have seen that the higher...

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Section 10.3 We have seen that the higher the confidence level, the wider the interval (because the Z value is higher). Ideally, we would like a high confidence level and a narrow interval. High confidence says that our method almost always gives correct answers. A narrow interval says that we have pinned down the parameter quite precisely. How can we get both at the same time? We need to now focus on the width of our confidence interval (and concentrate on how to get it narrower). If our confidence interval is too wide, then it is not telling us very much information. The margin of error determines the width of the interval. margin of error = z n σ If we want to make the interval smaller, we need to make the margin of error smaller. Which of these factors can affect the width of the interval? σ is fixed and cannot be changed, so it is not a contender. What about z and n ?

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If n gets larger, the margin of error gets smaller, which means the interval gets smaller. Example 10.1 page 309
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This note was uploaded on 04/06/2008 for the course MTHSC 309 taught by Professor Cathydavis during the Spring '08 term at Clemson.

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Stats 309 10-3 - Section 10.3 We have seen that the higher...

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