1. A confidence interval for a population mean has a margin of error of 10.7. What is the length of the confidence interval?
2. A random sample of size 17 is taken from a population. A normal probability plot of the sample data is found to be very close to linear. The population standard deviation is unknown. The appropriate method for obtaining the confidence interval is the z-interval procedure. Is this true?
3. A variable of a population has a mean of 266, and a standard deviation of 16... Ten observations of this variable have a mean of 262.1 and a sample standard deviation of 20.4. The observed value of the standardized version of x-bar is z =-.77, and the studentized version of x-bar is t = -0.605. Is this true? Show answers.

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1. A confidence interval for a population mean has a margin of error of 10.7. What is the length of the confidence interval?

As we know that a confidence interval is equal to
(sample mean -margin of error, sample mean + margin of error)

Hence, the length of the confidence interval is equal to
2*margin of error.

If a confidence interval for a population mean has a ...

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2.
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12,000 18,000 30,000 60,000 14,000 10,500 52,000