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The heights of young American women, in inches, are Normally distributed a with mean of u and a standard deviation of o=2.4. 31. The margin of error for a 99% confidence interval is desired to be t1 inch. What should be the sample size? A) 7 B) 22 C) 38 D) 39

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Jarrod Robel
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29 Jan 2018
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An agricultural researcher plants 25 plots with a new variety of yellow corn. Assume that the yield per acre for the new variety of yellow corn follows a Normal distribution with an unknown mean of u and a standard deviation of o= 10 bushels per acre. 24. Which of the following would produce a confidence interval with a smaller margin of error than the 90% confidence interval? A) Plant only five plots rather than 25, because five are easier to manage and control. B) Plant 10 plots rather than 25, because a smaller sample size will result in a smaller margin of error. C) Plant 100 plots rather than 25, because a larger sample size will result in a smaller margin of error. Compute a 99% confidence interval rather than a 90% confidence interval, because a higher confidence level will result in a smaller margin of error.

It is known that driving can be difficult in regions where winter conditions involve snow-covered roads. For cars equipped with all-season tires traveling at 90 km/hr, the mean stopping time in fresh snow is known to be 215 meters with a standard deviation of o = 2.5 meters. It is often advocated that automobiles in such areas should be equipped with special tires to compensate for such conditions, especially with respect to stopping distance. A manufacturer of tires made for driving in fresh snow claims that vehicles equipped with their tires have a decreased stopping distance. A study was done using a random sample of 9 snow tires from the manufacturer on a snow-covered test track. The tests resulted in a mean stopping distance of t = 212.9 meters. 29. Using the sample results and assuming that stopping distance is a Normally distributed random variable, what is the value of the test statistic? A) 0.05 B) -2.52 C) -9.36 D) -1.04 E) -1.96

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