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# Sometimes c never 74 if a null hypothesis is rejected

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Unformatted text preview: airline company is concerned that its proportion of late arrivals has substantially increased in the past month. Historical data shows that on the average 18% of the company airplanes have arrived late. In a random sample of 1,240 airplanes, 310 airplanes have arrived late. If we are conducting a hypothesis test of a single proportion to determine if the proportion of late arrivals has increased: What is the value of the calculated test statistic? A. Z = 6.416 B. Z = 3.208 C. Z = -3.208 D. Z = -6.416 E. Z = 1.833 84. A mail-order business prides itself in its ability to fill customers' orders in less than six calendar days, on average. Periodically, the operations manager selects a random sample of customer orders and determines the number of days required to fill the orders. On one occasion when a sample of 39 orders was selected, the average number of days was 6.65 with a sample standard deviation of 1.5 days. Calculate the appropriate test statistic to test the hypotheses. A. 2.71 B. 16.90 C. 0.65 D. -2.71 E. 3.31 1-730 Chapter 01 - An Introduction to Business Statistics 85. A mail-order business prides itself in its ability to fill customers' orders in less than six calendar days, on average. Periodically, the operations manager selects a random sample of customer orders and determines the number of days required to fill the orders. On one occasion when a sample of 39 orders was selected, the average number of days was 6.65 with a sample standard deviation of 1.5 days. What is the critical value for α = .10 to test the hypotheses. A. -1.28 B. -1.96 C. -2.33 D. 1.28 E. 1.96 86. A random sample of 80 companies who announced corrections to their balance sheets took a mean time of 8.1 days for the time between balance sheet construction and the complete audit. The standard deviation of these times was 1.3 days. If the claim is that the population mean is greater than 7.5 days, calculate the appropriate test statistic to test the hypotheses. A. -4.13 B. 36.92 C. 4.71 D. -4.71 E. 4.13 87. A random sample of 80 companies who announced corrections to their balance sheets took a mean time of 8.1 days for the time between balance sheet construction and the complete audit. The standard deviation of these times was 1.3 days. What is the critical value for α = .001 to test the claim that µ is greater than 7.5 days. A. 2.575 B. 3.09 C. -1.96 D. -2.575 E. -3.09 1-731 Chapter 01 - An Introduction to Business Statistics 88. The manufacturer of an over-the-counter heartburn relief mediation claims that its product brings relief in less than 3.5 minutes, on average. To be able to make this claim the manufacturer was required by the FDA to present statistical evidence in support of the claim. The manufacturer reported that for a sample of 50 heartburn sufferers, the mean time to relief was 3.3 minutes and the standard deviation was 1.1 minutes. Calculate the appropriate test statistic to test the hypotheses. A. 1.29 B. 9.09 C. -1.29 D. -2.58 E. -9.09 89. The manufacturer of an over-the-counter heartburn relief mediation claims that its product brings relief in less than 3.5 minutes, on average. To be able to make this claim the manufacturer was required by the FDA to present statistical evidence in support of the claim. The manufacturer reported that for a sample of 50 heartburn sufferers, the mean time to relief was 3.3 minutes and the standard deviation was 1.1 minutes. Calculate the p-value that corresponds to the test statistic. A. 0.0985 B. 0.0001 C. 0.4015 D. 0.005 E. -0.985 90. A company has developed a new ink-jet cartridge for its printer that it believes has a longer life-time on average than the one currently being produced. To investigate its length of life, 225 of the new cartridges were tested by counting the number of high-quality printed pages each was able to produce. The sample mean and standard deviation were determined to be 1511.4 pages and 35.7 pages, respectively. The historical average lifetime for cartridges produced by the current process is 1502.5 pages. Calculate the appropriate test statistic to test the hypotheses. A. 56.09 B. 3.74 C. 22.34 D. -3.74 E. -22.34 1-732 Chapter 01 - An Introduction to Business Statistics 91. A company has developed a new ink-jet cartridge for its printer that it believes has a longer life-time on average than the one currently being produced. To investigate its length of life, 225 of the new cartridges were tested by counting the number of high-quality printed pages each was able to produce. The sample mean and standard deviation were determined to be 1511.4 pages and 35.7 pages, respectively. The historical average lifetime for cartridges produced by the current process is 1502.5 pages. What is the critical value for α = .05 to test the hypotheses. A. 1.645 B. -1.645 C. 1.96 D. 1.28 E. -1.96 92. When 100 randomly selected car owners are surveyed, it is found that the mean length of time they plan to keep their car is 7.01 years, and the standard deviation is 3.74...
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