STATISTICAL TECHNIQUES AND TOOLS
CONFIDENCE INTERVALS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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z confidence interval for a mean
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t confidence interval for a mean
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z confidence interval for a proportion
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t confidence interval for a proportion
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Detailed explanation-1: -ANSWER: (a) No. Since 0.037 < 0.05, 30 is not in the 95% confidence interval.
Detailed explanation-2: -The 95% confidence interval defines a range of values that you can be 95% certain contains the population mean. With large samples, you know that mean with much more precision than you do with a small sample, so the confidence interval is quite narrow when computed from a large sample.
Detailed explanation-3: -A 99% confidence interval will allow you to be more confident that the true value in the population is represented in the interval. However, it gives a wider interval than a 95% confidence interval. For most analyses, it is acceptable to use a 95% confidence interval to extend your results to the general population.