## MATH 221 Week 7 Quiz (Fall 2018)

**Question**: (CO6) From a random sample of 68 businesses, it is found that the mean time that employees spend on personal issues each week is 45.8 hours with a standard deviation of 0.35 hours. What is the 95% confidence interval for the amount of time spent on personal issues?**Question**: If a confidence interval is given from 8.50 to 10.25 and the mean is known to … 9.375, what is the maximum error?**Question**: (CO6) If the standard deviation of a sample decreases without other changes, what is most likely to happen to the confidence interval?**Question**: (CO6) From a random sample of 41 teens, it is found that on average they spend 43.1 hours each week online with a standard deviation of 5.91 hours. What is the 90% confidence interval for the amount of time they spend online each week?**Question**: (CO6) A company making refrigerators strives for the internal temperature to have a mean of 37.5 degrees with a standard deviation of 0.6 degrees, based on samples of 100. A sample of 100 refrigerators have an average temperature of 37.53 degrees. Are the refrigerators within the 90% confidence interval?**Question**: (CO6) What is the 97% confidence interval for a sample of 104 soda cans that have a mean amount of 15.10 ounces and a standard deviation of 0.08 ounces?**Question**: (CO6) Determine the minimum sample size required when you want to … 98% confident that the sample mean is within two units of the population mean. Assume a standard deviation of 4.82 in a normally distributed population.**Question**: (CO6) Determine the minimum sample size required when you want to … 80% confident that the sample mean is within 1.3 units of the population mean. Assume a standard deviation of 9.24 in a normally distributed population.**Question**: (CO6) Determine the minimum sample size required when you want to … 75% confident that the sample mean is within fifteen units of the population mean. Assume a standard deviation of 327.8 in a normally distributed population.**Question**: (CO6) In a sample of 8 high school students, they spent an average of 28.8 hours each week doing sports with a standard deviation of 3.2 hours. Find the 95% confidence interval.**Question**: (CO6) In a sample of 15 stuffed animals, you find that they weigh an average of 8.56 ounces with a standard deviation of 0.09 ounces. Find the 92% confidence interval.**Question**: (CO6) Market research indicates that a new product has the potential to make the company an additional $3.8 million, with a standard deviation of $1.8 million. If this estimate was based on a sample of 10 customers, what would … the 90% confidence interval?**Question**: (CO6) Supplier claims that they are 95% confident that their products will … in the interval of 20.45 to 21.05. You take samples and find that the 95% confidence interval of what they are sending is 20.48 to 21.02. What conclusion can … made?**Question**: (CO6) In a sample of 17 small candles, the weight is found to … 3.72 ounces with a standard deviation of 0.963 ounces. What would … the 87% confidence interval for the size of the candles?**Question**: (CO6) In a situation where the standard deviation was increased from 3.1 to 5.8, what would … the impact on the confidence interval?**Question**: (CO7) A company claims that its heaters last at most 5 years. Write the null and alternative hypotheses and note which is the claim.**Question**: (CO7) An executive claims that her employees spend more than 2.5 hours each week in meetings. Write the null and alternative hypotheses and note which is the claim.**Question**: (CO7) In hypothesis testing, a key element in the structure of the hypotheses is that the claim is ____ .**Question**: (CO7) A landscaping company claims that at least 90% of workers arrive on time. If a hypothesis test is performed that fails to reject the null hypothesis, how would this decision … interpreted?**Question**: (CO7) A textbook company claims that their book is so engaging that more than 55% of students read it. If a hypothesis test is performed that rejects the null hypothesis, how would this decision … interpreted?**Question**: (CO7) An advocacy group claims that the mean braking distance of a certain type of tire is 75 feet when the car is going 40 miles per hour. In a test of 45 of these tires, the braking distance has a mean of 78 and a standard deviation of 5.9 feet. Find the standardized test statistic and the corresponding p-value.**Question**: (CO7) The heights of 82 roller coasters have a mean of 281.4 feet and a standard deviation of 59.3 feet. Find the standardized tests statistics and the corresponding p-value when the claim is that roller coasters are more than 290 feet tall.**Question**: (CO7) A light bulb manufacturer guarantees that the mean life of a certain type of light bulb is at least 720 hours. A random sample of 51 light bulbs as a mean of 705.4 hours with a standard deviation of 62 hours. At an α=0.05, can you support the company’s claim using the test statistic?**Question**: (CO7) A restaurant claims the customers receive their food in less than 16 minutes. A random sample of 39 customers finds a mean wait time for food to … 15.8 minutes with a standard deviation of 0.7 minutes. At α = 0.04, can you support the organizations’ claim using the test statistic?**Question**: (CO7) A manufacturer claims that their calculators are 6.800 inches long. A random sample of 55 of their calculators finds they have a mean of 6.812 inches with a standard deviation of 0.05 inches. At α=0.08, can you support the manufacturer’s claim using the p value?**Question**: (CO7) A travel analyst claims that the mean room rates at a three-star hotel in Chicago is greater than $152. In a random sample of 36 three- star hotel rooms in Chicago, the mean room rate is $165 with a standard deviation of $41. At α=0.10, what type of test is this and can you support the analyst’s claim using the p-value?**Question**: (CO7) A car company claims that the mean gas mileage for its luxury sedan is at least 24 miles per gallon. A random sample of 7 cars has a mean gas mileage of 23 miles per gallon and a standard deviation of 1.1 miles per gallon. At α=0.05, can you support the company’s claim?**Question**: (CO7) A state Department of Transportation claims that the mean wait time for various services at its different location is less than 6 minutes. A random sample of 16 services at different locations has a mean wait time of 9.5 minutes and a standard deviation of 7.6 minutes. At α=0.05, can the department’s claim … supported?**Question**: (CO7) A used car dealer says that the mean price of a three-year-old sport utility vehicle in good condition is $18,000. A random sample of 20 such vehicles has a mean price of $18,450 and a standard deviation of $1140. At α=0.08, can the dealer’s claim … supported?**Question**: (CO7) A researcher wants to determine if lead levels are different between the top of a glass of water and the bottom of a glass of water. Many samples of water are taken. From half, the lead level at the top is measured and from half, the lead level at the bottom is measured. Would this … a valid matched pair test?

Play Video