Q&A Hero

Q: Suppose an airline decides to conduct a survey of its customers to determine their opinion of a proposed one-bag limit. The plan calls for a random sample of customers on different flights to be given a short written survey to complete during the flight. One key question on the survey will be: "Do you approve of limiting the number of carry-on bags to a maximum of one bag?" Airline managers expect that only about 15% will say "yes." Based on this assumption, what size sample should the airline take if it wants to develop a 95% confidence interval estimate for the population proportion who will say "yes" with a margin of error of 0.02? A) 1151 B) 1341 C) 1512 D) 1225

Q: Most major airlines allow passengers to carry two pieces of luggage (of a certain maximum size) onto the plane. However, their studies show that the more carry-on baggage passengers have, the longer it takes to unload and load passengers. One regional airline is considering changing its policy to allow only one carry-on per passenger. Before doing so, it decided to collect some data. Specifically, a random sample of 1,000 passengers was selected. The passengers were observed, and the number of bags carried on the plane was noted. Out of the 1,000 passengers, 345 had more than one bag. Suppose the airline also noted whether the passenger was male or female. Out of the 1,000 passengers observed, 690 were males. Of this group, 280 had more than one bag. Using this data, obtain and interpret a 95% confidence interval estimate for the proportion of male passengers in the population who would have been affected by the one-bag limit. A) (0.2815, 0.5124) B) (0.3361, 0.4712) C) (0.3692, 0.4424) D) (0.3814, 0.4125)

Q: Most major airlines allow passengers to carry two pieces of luggage (of a certain maximum size) onto the plane. However, their studies show that the more carry-on baggage passengers have, the longer it takes to unload and load passengers. One regional airline is considering changing its policy to allow only one carry-on per passenger. Before doing so, it decided to collect some data. Specifically, a random sample of 1,000 passengers was selected. The passengers were observed, and the number of bags carried on the plane was noted. Out of the 1,000 passengers, 345 had more than one bag. The domestic version of Boeing's 747 has a capacity for 568 passengers. Determine an interval estimate of the number of passengers that you would expect to carry more than one piece of luggage on the plane. Assume the plane is at its passenger capacity. A) (171.651, 216.214) B) (174.412, 217.218) C) (181.514, 208.313) D) (179.20, 212.716)

Q: Most major airlines allow passengers to carry two pieces of luggage (of a certain maximum size) onto the plane. However, their studies show that the more carry-on baggage passengers have, the longer it takes to unload and load passengers. One regional airline is considering changing its policy to allow only one carry-on per passenger. Before doing so, it decided to collect some data. Specifically, a random sample of 1,000 passengers was selected. The passengers were observed, and the number of bags carried on the plane was noted. Out of the 1,000 passengers, 345 had more than one bag. Based on this sample, develop and interpret a 95% confidence interval estimate for the proportion of the traveling population that would have been impacted had the one-bag limit been in effect. A) (0.3155, 0.3745) B) (0.3220, 0.3680) C) (0.3216, 0.3684) D) (0.3336, 0.3564)

Q: A survey of 499 women for the American Orthopedic Foot and Ankle Society revealed that 38% wear flats to work. Suppose the society also wishes to estimate the proportion of women who wear athletic shoes to work with a margin of error of 0.01 with 95% confidence. Determine the sample size required. A) 7241 B) 9604 C) 10021 D) 9715

Q: A survey of 499 women for the American Orthopedic Foot and Ankle Society revealed that 38% wear flats to work. Use this sample information to develop a 99% confidence interval for the population proportion of women who wear flats to work. A) (0.324, 0.436) B) (0.302, 0.458) C) (0.368, 0.392) D) 0.363, 0.397)

Q: As the automobile accident rate increases, insurers are forced to increase their premium rates. Companies such as Allstate have recently been running a campaign they hope will result in fewer accidents by their policyholders. For each six-month period that a customer goes without an accident, Allstate will reduce the customer's premium rate by a certain percentage. Companies like Allstate have reason to be concerned about driving habits, based on a survey conducted by Drive for Life, a safety group sponsored by Volvo of North America, in which 1,100 drivers were surveyed. Among those surveyed, 74% said that careless or aggressive driving was the biggest threat on the road. One-third of the respondents said that cell phone usage by other drivers was the driving behavior that annoyed them the most. Based on these data, assuming that the sample was a simple random sample, construct and interpret a 95% confidence interval estimate for the true proportion in the population of all drivers who are annoyed by cell phone users. A) (0.313, 0.347) B) (0.306, 0.354) C) (0.302, 0.358) D) (0.316, 0.344)

Q: At issue is the proportion of people in a particular county who do not have health care insurance coverage. A simple random sample of 240 people was asked if they have insurance coverage, and 66 replied that they did not have coverage. Based on these sample data, determine the 95% confidence interval estimate for the population proportion. A) (0.239, 0.321) B) (0.259, 0.301) C) (0.224, 0.336) D) (0.268, 0.292)

Q: A decision maker is interested in estimating a population proportion. A sample of size n = 150 yields 115 successes. Based on these sample data, construct a 90% confidence interval estimate for the true population proportion. A) (0.714, 0.826) B) (0.717, 0.823) C) (0.737, 0.803) D) (0.750, 0.790)

Q: A pilot sample of 75 items was taken, and the number of items with the attribute of interest was found to be 15. How many more items must be sampled to construct a 99% confidence interval estimate for p with a 0.025 margin of error? A) 1512 B) 1612 C) 1698 D) 1623

Q: Compute the 90% confidence interval estimate for the population proportion, p, based on a sample size of 100 when the sample proportion, is equal to 0.40. A) 0.3880, 0.0412) B) (0.3930, 0.4070) C) (0.3194, 0.4806) D) (0.3886, 0.4114)

Q: A public policy research group is conducting a study of health care plans and would like to estimate the average dollars contributed annually to health savings accounts by participating employees. A pilot study conducted a few months earlier indicated that the standard deviation of annual contributions to such plans was $1,225. The research group wants the study's findings to be within $100 of the true mean with a confidence level of 90%. What sample size is required? A) 407 B) 361 C) 512 D) 546

Q: A production process that fills 12-ounce cereal boxes is known to have a population standard deviation of 0.009 ounce. If a consumer protection agency would like to estimate the mean fill, in ounces, for 12-ounce cereal boxes with a confidence level of 92% and a margin of error of 0.001, what size sample must be used? A) 249 B) 351 C) 512 D) 211

Q: Suppose a study estimated the population mean for a variable of interest using a 99% confidence interval. If the width of the estimated confidence interval (the difference between the upper limit and the lower limit) is 600 and the sample size used in estimating the mean is 1,000, what is the population standard deviation? A) 26711.14 B) 2451.23 C) 3684.21 D) 5125.11

Q: A manager wishes to estimate a population mean using a 95% confidence interval estimate that has a margin of error of 44.0. If the population standard deviation is thought to be 680, what is the required sample size? A) 1215 B) 871 C) 1050 D) 918

Q: An advertising company wishes to estimate the mean household income for all single working professionals who own a foreign automobile. If the advertising company wants a 90% confidence interval estimate with a margin of error of $2,500, what sample size is needed if the population standard deviation is known to be $27,500? A) 156 B) 328 C) 251 D) 415

Q: What sample size is needed to estimate a population mean within 50 of the true mean value using a confidence level of 95%, if the true population variance is known to be 122,500? A) 211 B) 155 C) 214 D) 189

Q: The file Danish Coffee contains a random sample of 144 Danish coffee drinkers and measures the annual coffee consumption in kilograms for each sampled coffee drinker. A marketing research firm wants to use this information to develop an advertising campaign to increase Danish coffee consumption. Develop and interpret a 90% confidence interval estimate for the mean annual coffee consumption of Danish coffee drinkers. A) (6.4257, 6.6479) B) (6.1768, 6.8968) C) (6.3881, 6.6855) D) (6.3366, 6.7370)

Q: The file Danish Coffee contains a random sample of 144 Danish coffee drinkers and measures the annual coffee consumption in kilograms for each sampled coffee drinker. A marketing research firm wants to use this information to develop an advertising campaign to increase Danish coffee consumption. Based on the sample's results, what is the best point estimate of average annual coffee consumption for Danish coffee drinkers? A) 6.5368 B) 7.4151 C) 6.1411 D) 7.4127

Q: Suppose a study of 196 randomly sampled privately insured adults with incomes over 200% of the current poverty level is to be used to measure out-of-pocket medical expenses for prescription drugs for this income class. The sample data are in the file Drug Expenses. Based on the sample data, construct a 95% confidence interval estimate for the mean annual out-of-pocket expenditures on prescription drugs for this income class. Interpret this interval. A) (162.08, 172.96) B) (163.50, 171.54) C) (164.19, 170.85) D) (161.97, 173.07)

Q: According to USA Today, customers are not settling for automobiles straight off the production lines. As an example, those who purchase a $355,000 Rolls-Royce typically add $25,000 in accessories. One of the affordable automobiles to receive additions is BMW's Mini Cooper. A sample of 179 recent Mini purchasers yielded a sample mean of $5,000 above the $20,200 base sticker price. Suppose the cost of accessories purchased for all Mini Coopers has a standard deviation of $1,500. Determine the margin of error in estimating the average cost of accessories on Mini Coopers. A) 219.75 B) 214.41 C) 231.14 D) 291.11

Q: According to USA Today, customers are not settling for automobiles straight off the production lines. As an example, those who purchase a $355,000 Rolls-Royce typically add $25,000 in accessories. One of the affordable automobiles to receive additions is BMW's Mini Cooper. A sample of 179 recent Mini purchasers yielded a sample mean of $5,000 above the $20,200 base sticker price. Suppose the cost of accessories purchased for all Mini Coopers has a standard deviation of $1,500. Calculate a 95% confidence interval for the average cost of accessories on Mini Coopers. A) (4850.33, 5149.67) B) (4878.82, 5121.18) C) (4788.86, 5211.14) D) (4780.25, 5219.75)

Q: Even before the record gas prices during the summer of 2008, an article written by Will Lester of the Associated Press reported on a poll in which 80% of those surveyed say that Americans who currently own a SUV (sport utility vehicle) should switch to a more fuel-efficient vehicle to ease America's dependency on foreign oil. This study was conducted by the Pew Research Center for the People & the Press. As a follow-up to this report, a consumer group conducted a study of SUV owners to estimate the mean mileage for their vehicles. A simple random sample of 91 SUV owners was selected, and the owners were asked to report their highway mileage. The following results were summarized from the sample data: = 18.2 mpg s = 6.3 mpg Based on these sample data, compute and interpret a 90% confidence interval estimate for the mean highway mileage for SUVs. A) (15.4, 21.0) B) (12.4, 24.0) C) (17.6, 18.8) D) (17.1, 19.3)

Q: Allante Pizza delivers pizzas throughout its local market area at no charge to the customer. However, customers often tip the driver. The owner is interested in estimating the mean tip income per delivery. To do this, she has selected a simple random sample of 12 deliveries and has recorded the tips that were received by the drivers. These data are: $2.25 $2.50 $2.25 $2.00 $2.00 $1.50 $0.00 $2.00 $1.50 $2.00 $3.00 $1.50 Suppose the owner is interested in developing a 90% confidence interval estimate. Given the fact that the population standard deviation is unknown, what distribution will be used to obtain the critical value? A) s-distribution B) t-distribution C) z-distribution D) k-distribution

Q: Allante Pizza delivers pizzas throughout its local market area at no charge to the customer. However, customers often tip the driver. The owner is interested in estimating the mean tip income per delivery. To do this, she has selected a simple random sample of 12 deliveries and has recorded the tips that were received by the drivers. These data are: $2.25 $2.50 $2.25 $2.00 $2.00 $1.50 $0.00 $2.00 $1.50 $2.00 $3.00 $1.50 Based on these sample data, what is the best point estimate to use as an estimate of the true mean tip per delivery? A) 1.875 B) 1.811 C) 1.50 D) 1.312

Q: Determine the 90% confidence interval estimate for the population mean of a normal distribution given n = 100, σ = 121, and = 1,200. A) (1186.31, 1213.69) B) (1180.10, 1219.90) C) (1182.56, 1217.44) D) (1191.12, 1208.88)

Q: Construct a 98% confidence interval estimate for the population mean given the following values: A) (113.41, 126.59) B) (117.46, 122.54) C) (113.67, 126.33) D) (113.13, 126.87)

Q: Construct a 95% confidence interval estimate for the population mean given the following values: A) (295.54, 304.56) B) (297.42, 302.58) C) (296.52, 303.48) D) (293.18, 306.82)

Q: Assuming the population of interest is approximately normally distributed, construct a 95% confidence interval estimate for the population mean given the following values: A) (16.73, 20.07) B) (13.22, 23.58) C) (15.86, 20.94) D) (14.20, 22.60)

Q: The chamber of commerce in a beach resort town wants to estimate the proportion of visitors who are repeat visitors. Suppose that they have estimated that they need a sample size of n=16,577 people to achieve a margin of error of .01 percentage points with 99 percent confidence, but this is too large a sample size to be practical. How can they reduce the sample size? A) Use a higher level of confidence B) Use a smaller margin or error C) Use a lower level of confidence D) Conduct a census

Q: A sample of 250 people resulted in a confidence interval estimate for the proportion of people who believe that the federal government's proposed tax increase is justified is between 0.14 and 0.20. Based on this information, what was the confidence level used in this estimation? A) Approximately 1.59 B) 95 percent C) Approximately 79 percent D) Can't be determined without knowing σ.

Q: Suppose that an internal report submitted to the managers at a bank in Boston showed that with 95 percent confidence, the proportion of the bank's customers who also have accounts at one or more other banks is between .45 and .51. Given this information, what sample size was used to arrive at this estimate? A) About 344 B) Approximately 1,066 C) Just under 700 D) Can't be determined without more information.

Q: A regional hardware chain is interested in estimating the proportion of their customers who own their own homes. There is some evidence to suggest that the proportion might be around 0.70. Given this, what sample size is required if they wish a 90 percent confidence level with a margin of error of .025? A) About 355 B) Approximately 910 C) Almost 1,300 D) 100

Q: The chamber of commerce in a beach resort town wants to estimate the proportion of visitors who are repeat visitors. From previous experience they believe the portion is not larger than 20 percent. They want to estimate the proportion to within 0.04 percentage points with 95 percent confidence. The sample size they should use is: A) n = 601 B) n = 97 C) n = 10 D) n = 385

Q: The chamber of commerce in a beach resort town wants to estimate the proportion of visitors who are repeat visitors. From previous experience they believe the portion is in the vicinity of 0.5 and they want to estimate the proportion to within 0.03 percentage points with 95 percent confidence. The sample size they should use is: A) n = 1068 B) n = 545 C) n = 33 D) n = 95

Q: A random sample of 340 people in Chicago showed that 66 listened to WJKT-1450, a radio station in South Chicago Heights. Based on this information, what is the upper limit for the 95 percent confidence interval estimate for the proportion of people in Chicago that listen to WJKT-1450? A) 1.96 B) Approximately 0.0009 C) About 0.2361 D) About 0.2298

Q: A random sample of 340 people in Chicago showed that 66 listened to WJKT-1450, a radio station in South Chicago Heights. Based on this sample information, what is the point estimate for the proportion of people in Chicago that listen to WJKT-1450? A) 340 B) About 0.194 C) 1450 D) 66

Q: The produce manager for a large retail food chain is interested in estimating the percentage of potatoes that arrive on a shipment with bruises. A random sample of 150 potatoes showed 14 with bruises. Based on this information, what is the margin of error for a 95 percent confidence interval estimate? A) 0.0933 B) 0.0466 C) 0.0006 D) Can't be determined without knowing σ.

Q: The administrator at Sacred Heart Hospital is interested in estimating the proportion of patients who are satisfied with the meals at the hospital. A random sample of 250 patients was selected and the patients were surveyed. Of these, 203 indicated that they were satisfied. Based on this, what is the estimate of the standard error of the sampling distribution? A) 0.8120 B) 0.0247 C) 0.0006 D) Can't be determined without knowing σ.

Q: A random sample of 121 automobiles traveling on an interstate showed an average speed of 65 mph. From past information, it is known that the standard deviation of the population is 22 mph. The 95 percent confidence interval for μ is determined as (61.08, 68.92). If we are to reduce the sample size to 100 (other factors remain unchanged), the 95 percent confidence interval for μ would: A) become wider. B) become narrower. C) be the same. D) be impossible to determine.

Q: Which of the following will result in a larger margin of error in an application involving the estimation of a population mean? A) Increasing the sample size B) Decreasing the confidence level C) Increasing the sample standard deviation D) All of the above

Q: An animal shelter wants to estimate the mean number of animals housed daily and they know the standard deviation. If they want to find a 98 percent confidence interval the critical value to use is: A) 1.645 B) 1.98 C) 2.33 D) 2.575

Q: A cell phone service provider has selected a random sample of 20 of its customers in an effort to estimate the mean number of minutes used per day. The results of the sample included a sample mean of 34.5 minutes and a sample standard deviation equal to 11.5 minutes. Based on this information, and using a 95 percent confidence level: A) the critical value is z = 1.96 B) the critical value is z = 1.645 C) the critical value is t = 2.093 D) The critical value can't be determined without knowing the margin of error.

Q: The U.S. Post Office is interested in estimating the mean weight of packages shipped using the overnight service. They plan to sample 300 packages. A pilot sample taken last year showed that the standard deviation in weight was about 0.15 pound. If they are interested in an estimate that has 95 percent confidence, what margin of error can they expect? A) Approximately 0.017 pound B) About 0.0003 pound C) About 1.96 D) Can't be determined without knowing the population mean.

Q: A study has indicated that the sample size necessary to estimate the average electricity use by residential customers of a large western utility company is 900 customers. Assuming that the margin of error associated with the estimate will be 30 watts and the confidence level is stated to be 90 percent, what was the value for the population standard deviation? A) 265 watts B) Approximately 547.1 watts C) About 490 watts D) Can't be determined without knowing the size of the population.

Q: A hospital emergency room has collected a sample of n = 40 to estimate the mean number of visits per day. It has found the standard deviation is 32. Using a 90 percent confidence level, what is its margin of error? A) Approximately 1.5 visits B) About 9.9 visits C) Approximately 8.3 visits D) About 1.3 visits

Q: A large Midwestern university is interested in estimating the mean time that students spend at the student recreation center per week. A previous study indicated that the standard deviation in time is about 40 minutes per week. If the officials wish to estimate the mean time within 10 minutes with a 90 percent confidence, what should the sample size be? A) 44 B) 62 C) 302 D) Can't be determined without knowing how many students there are at the university.

Q: If a manager believes that the required sample size is too large for a situation in which she desires to estimate the mean income of blue collar workers in a state, which of the following would lead to a reduction in sample size? A) Reduce the level of confidence B) Allow a higher margin of error C) Somehow reduce the variation in the population D) All of the above

Q: A traffic engineer plans to estimate the average number of cars that pass through an intersection each day. Based on previous studies the standard deviation is believed to be 52 cars. She wants to estimate the mean to within 10 cars with 90 percent confidence. The needed sample size for n is: A) n = 104 days. B) n = 74 days. C) n = 10 days. D) n = 9 days.

Q: Past experience indicates that the variance in the time it takes for a "fast lube" operation to actually complete the lube and oil change for customers is 9.00 minutes. The manager wishes to estimate the mean time with 99 percent confidence and a margin of error of 0.50 minutes. Given this, what must the sample size be? A) n = 239 B) n = 2149 C) n = 139 D) n = 1245

Q: The purpose of a pilot sample is: A) to provide a better idea of what the population mean will be. B) to help clarify how the sampling process will be performed. C) to provide an idea of what the population standard deviation might be. D) to save time and money instead of having to carry out a full sampling plan.

Q: A major tire manufacturer wishes to estimate the mean tread life in miles for one of its tires. It wishes to develop a confidence interval estimate that would have a maximum sampling error of 500 miles with 90 percent confidence. A pilot sample of n = 50 tires showed a sample standard deviation equal to 4,000 miles. Based on this information, the required sample size is: A) 124. B) 246. C) 174. D) 196.

Q: The Hilbert Drug Store owner plans to survey a random sample of his customers with the objective of estimating the mean dollars spent on pharmaceutical products during the past three months. He has assumed that the population standard deviation is known to be $15.50. Given this information, what would be the required sample size to estimate the population mean with 95 percent confidence and a margin of error of $2.00? A) 231 B) 163 C) 16 D) 15

Q: When σ is unknown, the margin of error is computed by using: A) normal distribution. B) t-distribution. C) the mean of the sample. D) The margin of error is also unknown.

Q: The following data represent a random sample of bank balances for a population of checking account customers at a large eastern bank. Based on these data, what is the 95 percent confidence interval estimate for the true population mean?$2,300$756$325$1,457$208$2,345$1,560$124$356$3,179$457$789$120$2,760$998$508$210$789A) Approximately $1,069 $484.41B) About $839.40 to $1,298.60C) Approximately $1,069 2.1098D) None of the above

Q: The following data represent a random sample of bank balances for a population of checking account customers at a large eastern bank. Based on these data, what is the critical value for a 95 percent confidence interval estimate for the true population mean? $2,300 $756 $325 $1,457 $208 $2,345 $1,560 $124 $356 $3,179 $457 $789 $120 $2,760 $998 $508 $210 $789 A) 1.96 B) 2.1009 C) 2.1098 D) None of the above

Q: A study was recently conducted to estimate the mean cholesterol for adult males over the age of 55 years. From a random sample of n = 10 men, the sample mean was found to be 242.6 and the sample standard deviation was 73.33. To find the 95 percent confidence interval estimate for the mean, the correct critical value to use is: A) 1.96 B) 2.2281 C) 2.33 D) 2.2622

Q: A study was recently conducted to estimate the mean cholesterol for adult males over the age of 55 years. The following random sample data were observed: 245 304 135 202 300 196 210 188 256 390 Given this information, what is the point estimate for the population mean? A) About 73.35 B) 102 C) About 242.6 D) Can't be determined without knowing the confidence level.

Q: The Internal Revenue Service (IRS) is interested in estimating the mean amount of money spent on outside tax service by income tax filers filing as single on their individual form. To do this, they have selected a random sample of n = 16 people from this population and surveyed them to determine the sample mean and sample standard deviation. The following information was observed: Given this information, what is the 95 percent confidence interval for the mean dollars spent on outside tax assistance by taxpayers who file as single? A) Approximately $72.19 - $105.01 B) About $22.97 - $154.23 C) Approximately $80.90 - $96.30 D) About $28.25 - $148.95

Q: The Wisconsin Dairy Association is interested in estimating the mean weekly consumption of milk for adults over the age of 18 in that state. To do this, they have selected a random sample of 300 people from the designated population. The following results were recorded: Given this information, if the leaders wish to estimate the mean milk consumption with 90 percent confidence, what is the approximate margin of error in the estimate? A) z = 1.645 B) 12.996 ounces C) 0.456 ounce D) 0.75 ounce

Q: An educational organization in California is interested in estimating the mean number of minutes per day that children between the age of 6 and 18 spend watching television per day. A previous study showed that the population standard deviation was 21.5 minutes. The organization selected a random sample of n = 200 children between the age of 6 and 18 and recorded the number of minutes of TV that each person watched on a particular day. The mean time was 191.3 minutes. If the leaders of the organization wish to develop an interval estimate with 95 percent confidence, what will the margin of error be? A) Approximately 1.52 minutes B) About 2.98 minutes C) z = 1.96 D) Approximately 42.14 minutes

Q: An educational organization in California is interested in estimating the mean number of minutes per day that children between the age of 6 and 18 spend watching television per day. A previous study showed that the population standard deviation was 21.5 minutes. The organization selected a random sample of n = 200 children between the age of 6 and 18 and recorded the number of minutes of TV that each person watched on a particular day. The mean time was 191.3 minutes. If the leaders of the organization wish to develop an interval estimate with 98 percent confidence, what would be the upper and lower limits of the interval estimate? A) Approximately 187.76 minutes - 194.84 minutes B) About 141.21 minutes - 241.40 minutes C) Approximately 188.3 minutes - 194.3 minutes D) None of the above

Q: An educational organization in California is interested in estimating the mean number of minutes per day that children between the age of 6 and 18 spend watching television per day. A previous study showed that the population standard deviation was 21.5 minutes. The organization selected a random sample of n = 200 children between the ages of 6 and 18 and recorded the number of minutes of TV that each person watched on a particular day. The mean time was 191.3 minutes. If the leaders of the organization wish to develop an interval estimate with 98 percent confidence, what critical value should be used? A) z = 1.645 B) t = 2.38 C) Approximately z = 2.33 D) Can't be determined without knowing the margin of error.

Q: When small samples are used to estimate a population mean, in cases where the population standard deviation is unknown: A) the t-distribution must be used to obtain the critical value. B) the resulting margin of error for a confidence interval estimate will tend to be fairly small. C) there will be a large amount of sampling error. D) None of the above

Q: If a decision maker wishes to reduce the margin of error associated with a confidence interval estimate for a population mean, she can: A) decrease the sample size. B) increase the confidence level. C) increase the sample size. D) use the t-distribution.

Q: A popular restaurant takes a random sample n = 25 customers and records how long each occupied a table. They found a sample mean of 1.2 hours and a sample standard deviation of 0.3 hour. Find the 95 percent confidence interval for the mean. A) 1.2 .118 B) 1.2 .124 C) 1.2 .588 D) 1.2 .609

Q: Which of the following statements is true with respect to the t-distribution? A) The t-distribution is symmetrical. B) The exact shape of the t-distribution depends on the number of degrees of freedom. C) The t-distribution is more spread out than the standard normal distribution. D) All of the above are true.

Q: In developing a confidence interval estimate for the population mean, the t-distribution is used to obtain the critical value when: A) the sample contains some extreme values that skew the results. B) the population standard deviation is unknown. C) the sampling that is being used is not a statistical sample. D) the confidence level is low.

Q: In a situation where the population standard deviation is known and we wish to estimate the population mean with 90 percent confidence, what is the appropriate critical value to use? A) z = 1.96 B) z = 2.33 C) z = 1.645 D) Can't be determined without knowing the degrees of freedom.

Q: Which of the following statements is true with respect to the confidence level associated with an estimation application? A) The confidence level is a percentage value between 50 and 100 that corresponds to the percentage of all possible confidence intervals, based on a given sample size, that will contain the true population value. B) The probability that the confidence interval estimate will contain the true population value. C) The degree of accuracy associated with the confidence interval estimate. D) None of the above

Q: The margin of error is: A) the largest possible sampling error at a specified level of confidence. B) the critical value multiplied by the standard error of the sampling distribution. C) Both A and B D) the difference between the point estimate and the parameter.

Q: In an effort to estimate the mean dollars spent per visit by customers of a food store, the manager has selected a random sample of 100 cash register receipts. The mean of these was $45.67 with a sample standard deviation equal to $12.30. Assuming that he wants to develop a 90 percent confidence interval estimate, the upper limit of the confidence interval estimate is: A) about $2.02 B) approximately $65.90 C) about $47.69 D) None of the above

Q: In an effort to estimate the mean dollars spent per visit by customers of a food store, the manager has selected a random sample of 100 cash register receipts. The mean of these was $45.67 with a sample standard deviation equal to $12.30. Assuming that he wants to develop a 90 percent confidence interval estimate, which of the following is the margin of error that will be reported? A) About $2.02 B) Nearly $50.20 C) $1.645 D) About $1.43

Q: Which of the following will increase the width of a confidence interval (assuming that everything else remains constant)? A) Decreasing the confidence level B) Increasing the sample size C) A decrease in the standard deviation D) Decreasing the sample size

Q: In developing a confidence interval estimate for the population mean, which of the following is true? A) The larger the sample standard deviation, the wider will be the interval estimate, all other things being equal. B) If the population standard deviation is unknown, the appropriate critical value should be obtained from the t-distribution. C) The confidence interval developed from a smaller sample size will have a larger margin of error than one obtained using a larger sample size, all other things being equal. D) All of the above are true.

Q: In an application to estimate the mean number of miles that downtown employees commute to work roundtrip each day, the following information is given: n = 20 = 4.33 s = 3.50 Based on this information, the upper limit for a 95 percent confidence interval estimate for the true population mean is: A) about 5.97 miles. B) about 7.83 miles. C) nearly 12.0 miles. D) about 5.86 miles.

Q: In an application to estimate the mean number of miles that downtown employees commute to work roundtrip each day, the following information is given: n = 20 = 4.33 s = 3.50 The point estimate for the true population mean is: A) 1.638 B) 4.33 1.638 C) 4.33 D) 3.50

Q: In an application to estimate the mean number of miles that downtown employees commute to work roundtrip each day, the following information is given: n = 20 = 4.33 s = 3.50 If the desired confidence level is 95 percent, the appropriate critical value is: A) z = 1.96 B) t = 2.093 C) t = 2.086 D) .7826

Q: The general format for a confidence interval is: A) point estimate z (standard deviation). B) point estimate (critical value)(standard error). C) margin of error (confidence coefficient) (standard error). D) point estimate (critical value)(standard deviation)

Q: Sampling error occurs when: A) a nonstatistical sample is used. B) the statistic computed from the sample is not equal to the parameter for the population. C) a random sample is used rather than a convenience sample. D) a confidence interval is used to estimate a population value rather than a point estimate.