As the length of the confidence interval for the population mean increases, the degree of confidence in the interval's actually containing the population mean a) does not change b) decreases c) increases Review Later Question 2 The gas mileage for a certain model of car is known to have a standard deviation of 4 mi/gallon. A simple random sample of 64 cars of this model is chosen and found to have a mean gas mileage of 27.5 mi/gallon. Construct a 96.5% confidence interval for the mean gas mileage for this car model. a) [19.068, 35.932] b) [26.594, 28.406] c) [26.446, 28.554] d) [27.368, 27.632] e) [20.252, 34.748] f) None of the above Review Later Question 3 If the 90% confidence limits for the population mean are 57 and 63, which of the following could be the 97% confidence limits a) [56, 64] b) [58, 65] c) [56, 61] d) [59, 63] e) [60, 60] f) None of the above Review Later Question 4 A 97% 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 1.7. The smallest sample size n that provides the desired accuracy is a) 164 b) 152 c) 142 d) 146 e) 141 f) None of the above Review Later Question 5 An SRS of 24 students at UH gave an average height of 6.1 feet and a standard deviation of .3 feet. Construct a 90% confidence interval for the mean height of students at UH. a) [4.600, 7.900] b) [6.079, 6.121] c) [5.995, 6.205] d) [5.586, 6.614] e) [4.850, 7.550] f) None of the above Review Later Question 6 Which test statistic should be used when computing a confidence interval given only the number in a sample, the population standard deviation and sample mean? a) b) t c) z Review Later Question 7 Location 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 above Review Later Question 8 An 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 A 45 48 46 48 52 50 49 Errors in B 31 37 39 37 54 45 49 40 45 41 50 Select a 90% confidence interval for the true mean difference in the two techniques. a) [3.050, 5.838] b) [4.183, 4.183] c) [2.584, 6.304] d) [2.195, 6.693] e) [0.261, 8.627] f) None of the above Review Later Question 9 A toy maker claims his best product has an average lifespan of exactly 18 years. A skeptical product evaluator asks for evidence (data) that might be used to evaluate this claim. The product evaluator was provided data collected from a random sample of 35 people who used the product. Using the data, an average product lifespan of 13 years and a standard deviation of 2 years was calculated. Select the 99%, confidence interval for the true mean lifespan of this product. a) [0.8722, 0.8722] b) [12.128, 13.872] c) [17.128, 18.872] d) [11.986, 14.014] e) [12.853, 13.147] f) None of the above Review Later Question 10 An important problem in industry is shipment damage. A pottery producing company 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 11. A random sample of 15 departing truckloads is selected at the delivery point and the average number of damaged items per truckload is calculated to be 11.3 with a calculated sample of variance of 0.64. Select a 90% confidence interval for the true mean of damaged items. a) [10.68, 11.92] b) [10.64, 11.36] c) [53.67, 33.86] d) [0.3635, 0.3635] e) [10.94, 11.66] f) None of the above