[answered] a) The standard deviation of test scores on a certain achie

a)?The standard deviation of test scores on a certain achievement test is 11.3. If a random sample of 81 students had a sample mean score of 74.6, find a 90 percent confidence interval estimate for the average score of all students.

b) A sample of 20 cigarettes is tested to determine nicotine content and the average?value observed was 1.2 mg. Compute a 99 percent two-sided confidence interval?for the mean nicotine content of a cigarette if it is known that the standard deviation?of a cigarette's nicotine content is ? = .2 mg.

c)?Suppose that a random sample of nine recently sold houses in a certain city resulted in a sample mean price of \$222,000, with a sample standard deviation of \$22,000. Give a 95 percent upper confidence interval for the mean price of all recently sold houses in this city.

1) For 90% confidence in terval 2)

The formula for a confidence interval for a population mean in a small sample is: (sample mean) ? t_?/2 * (standard deviation / ?n)

Where t_?/2 is the number...

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This question was answered on: Sep 18, 2020

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