STATISTICAL TECHNIQUES AND TOOLS
CONFIDENCE INTERVALS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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The lifetime of a certain type of batter is known to be normally distributed with a standard deviation of 20 hours. A sample of 50 batteries had a mean lifetime of 120.1 hours. It is desired to construct a 99% confidence interval for the mean lifetime of this type of battery.What is the Confidence Interval to one decimal place?
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(114.5, 125.6)
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(112.8, 127.4)
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(112.82, 127.38)
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(114.56, 125.64)
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Explanation:
Detailed explanation-1: -If we want to be 95% confident, we need to build a confidence interval that extends about 2 standard errors above and below our estimate. More precisely, it’s actually 1.96 standard errors. This is called a critical value (z*).
Detailed explanation-2: -A 95% confidence interval estimate for a population mean is determined to be 75 to 85. If the confidence level is reduced to 80%, the confidence interval for becomes narrower.
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