Chapter 9: Q. 1 (page 563)
Mr. Tabor believes that less than of the students at his school completed their math homework last night. The math teachers inspect the homework assignments from a random sample of students at the school.
Chapter 9: Q. 1 (page 563)
Mr. Tabor believes that less than of the students at his school completed their math homework last night. The math teachers inspect the homework assignments from a random sample of students at the school.
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1 A software company is trying to decide whether to produce an upgrade of one of its programs. Customers would have to pay for the upgrade. For the upgrade to be profitable, the company must sell it to more than of their customers. You contact a random sample of customers and find that would be willing to pay for the upgrade.
a. Do the sample data give convincing evidence that more than of the company’s customers are willing to purchase the upgrade? Carry out an appropriate test at the significance level.
b. Which would be a more serious mistake in this setting—a Type I error or a Type II error? Justify your answer.
c. Suppose that 30% of the company’s customers would be willing to pay for the upgrade. The power of the test to detect this fact is Interpret this value.
How much juice? Refer to Exercise 3. The mean amount of liquid in the bottles is ml and the standard deviation is ml. A significance test yields a -value of . Interpret the -value.
Upscale restaurant You are thinking about opening a restaurant and are searching for a good location. From the research you have done, you know that the mean income of those living near the restaurant must be over to support the type of upscale restaurant you wish to open. You decide to take a simple random sample of people living near one potential site. Based on the mean income of this sample, you will perform a test at the
significance level of versus , where is the true mean income in the population of people who live near the restaurant. The power of the test to detect that is Interpret this value.
Making conclusions A student performs a test of versus
at the significance level and gets a -value of . The
student writes: “Because the -value is small, we reject . The data prove that is true.” Explain what is wrong with this conclusion.
Fair coin? You want to determine if a coin is fair. So you toss it times and record the proportion of tosses that land “heads.” You would like to perform a test of versus , where = the proportion of all tosses of the
coin that would land “heads.” Check if the conditions for performing the significance test are met.
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