Bussiness St8Tics
One sample tests of hypotheses
1. An automobile manufacturer claims that a particular model gets 28 miles to the gallon. The Environmental Protection Agency, using a sample of 49 automobiles of this model, finds the sample mean to be 26.8 miles per gallon. From previous studies, the population standard deviation is known to be 5 miles per gallon. Could we reasonably expect that we could select such a sample if indeed the population mean is actually 28 miles per gallon?
2. Computing World has asserted that the amount of time owners of personal computers spend on their machines averages 23.9 hours per week and has a standard deviation of 12.6 hours per week. A random sampling of 81 of its subscribers revealed a sample mean usage of 27.2 hours per week. On the basis of this sample, is it reasonable to conclude that Computing World's subscribers are different from average personal computer owners?
3. A grocery store has specially packaged oranges and has claimed a bag of oranges will yield 2.5 quarts of juice. After randomly selecting 42 bags, a stocker found the average juice production per bag to be 2.2 quarts. Historically, we know the population standard deviation is 0.2 quart. Using this sample and a decision criterion of 1.96 standard errors, could we conclude the store's claims are correct?
4. Martha Inman, a highway safety engineer, decides to test the load-bearing capacity of a bridge that is 20 years old. Considerable data are available from similar tests on the same type of bridge. Which is appropriate, a one-tailed or a two-tailed test? If the minimum load-bearing capacity of this bridge must be 10 tons, what are the null and alternative hypotheses?
5. Dr. Ross Darrow believes that nicotine in cigarettes causes cigarette smokers to have higher daytime heart rates on average than do nonsmokers. He also believes that smokers crave the nicotine in cigarettes rather than just smoking for the physical satisfaction of the act and, accordingly, that the
1. An automobile manufacturer claims that a particular model gets 28 miles to the gallon. The Environmental Protection Agency, using a sample of 49 automobiles of this model, finds the sample mean to be 26.8 miles per gallon. From previous studies, the population standard deviation is known to be 5 miles per gallon. Could we reasonably expect that we could select such a sample if indeed the population mean is actually 28 miles per gallon?
2. Computing World has asserted that the amount of time owners of personal computers spend on their machines averages 23.9 hours per week and has a standard deviation of 12.6 hours per week. A random sampling of 81 of its subscribers revealed a sample mean usage of 27.2 hours per week. On the basis of this sample, is it reasonable to conclude that Computing World's subscribers are different from average personal computer owners?
3. A grocery store has specially packaged oranges and has claimed a bag of oranges will yield 2.5 quarts of juice. After randomly selecting 42 bags, a stocker found the average juice production per bag to be 2.2 quarts. Historically, we know the population standard deviation is 0.2 quart. Using this sample and a decision criterion of 1.96 standard errors, could we conclude the store's claims are correct?
4. Martha Inman, a highway safety engineer, decides to test the load-bearing capacity of a bridge that is 20 years old. Considerable data are available from similar tests on the same type of bridge. Which is appropriate, a one-tailed or a two-tailed test? If the minimum load-bearing capacity of this bridge must be 10 tons, what are the null and alternative hypotheses?
5. Dr. Ross Darrow believes that nicotine in cigarettes causes cigarette smokers to have higher daytime heart rates on average than do nonsmokers. He also believes that smokers crave the nicotine in cigarettes rather than just smoking for the physical satisfaction of the act and, accordingly, that the