# MATH 17282-As the length of the confidence interval for

Question 1As the length of the confidence interval for the population mean decreases, the degree of confidence in the interval’s actually containing the population meana) decreasesb) increasesc) does not changeReview LaterQuestion 2The gas mileage for a certain model of car is known to have a standard deviation of 5 mi/gallon. A simple random sample of 64 cars of this model is chosen and found to have a mean gas mileage of 28.4 mi/gallon. Construct a 97.8% confidence interval for the mean gas mileage for this car model.a) [27.141, 29.659]b) [26.969, 29.831]c) [28.221, 28.579]d) [16.950, 39.850]e) [18.330, 38.470]f) None of the aboveReview LaterQuestion 3If the 90% confidence limits for the population mean are 56 and 64, which of the following could be the 97% confidence limitsa) [59, 63]b) [55, 65]c) [56, 61]d) [58, 65]e) [59, 61]f) None of the aboveReview LaterQuestion 4A 95% confidence interval for the mean of a population is to be constructed and must be accurate to within 0.3 unit. A preliminary sample standard deviation is 1.2. The smallest sample size n that provides the desired accuracy isa) 50b) 62c) 58d) 68e) 57f) None of the aboveReview LaterQuestion 5An SRS of 28 students at UH gave an average height of 5.9 feet and a standard deviation of .1 feet. Construct a 90% confidence interval for the mean height of students at UH.a) [5.868, 5.932]b) [4.400, 7.700]c) [5.730, 6.070]d) [4.650, 7.350]e) [5.894, 5.906]f) None of the aboveReview LaterQuestion 6Which test statistic should be used when computing a confidence interval given only the number in a sample, the sample mean and sample standard deviation?a) zb) tc) ?Review LaterQuestion 7Location is known to affect the number, of a particular item, sold by an automobile dealer. Two different locations, A and B, are selected on an experimental basis. Location A was observed for 9 days and location B was observed for 13 days. The number of the particular items sold per day was recorded for each location. On average, location A sold 39 of these items with a sample standard deviation of 9 and location B sold 51 of these items with a sample standard deviation of 6. Select a 95% confidence interval for the difference in the true means of items sold at location A and B.a) [-19.16, -4.84]b) [44.34, 57.66]c) [83.34, 96.66]d) [-15.18, -8.815]e) [32.34, 45.66]f) None of the aboveReview LaterQuestion 8An auditor for a hardware store chain wished to compare the efficiency of two different auditing techniques. To do this he selected a sample of nine store accounts and applied auditing techniques A and B to each of the nine accounts selected. The number of errors found in each of techniques A and B is listed in the table below:Errors in AErrors in B453148374639483752545045494940414550Select a 99% confidence interval for the true mean difference in the two techniques.a) [-7.557, 7.557]b) [-3.113, 12.001]c) [2.195, 6.693]d) [1.084, 7.804]e) [1.925, 6.963]f) None of the aboveReview LaterQuestion 9A shoemaker claims his best product has an average lifespan of exactly 18 years. A skeptical customer asks for evidence (data) that might be used to evaluate this claim. The customer was provided data collected from a random sample of 50 people who used the product. Using the data, an average product lifespan of 13 years and a standard deviation of 4 years was calculated. Select the 95%, confidence interval for the true mean lifespan of this product.a) [12.843, 13.157]b) [16.891, 19.109]c) [11.891, 14.109]d) [-1.1087, 1.1087]e) [11.303, 14.697]f) None of the aboveReview LaterQuestion 10An important problem in industry is shipment damage. A windshield factory ships its product by truck and determines that it cannot meet its profit expectations if, on average, the number of damaged items per truckload is greater than 12. A random sample of 12 departing truckloads is selected at the delivery point and the average number of damaged items per truckload is calculated to be 9.4 with a calculated sample of variance of 0.64. Select a 99% confidence interval for the true mean of damaged items.a) [8.682, 10.12]b) [39.48, -25.66]c) [11.28, 12.72]d) [-0.7181, 0.7181]e) [8.707, 10.09]f) None of the above