Practical Business Statistics 7th Edition Andrew Siegel - Solutions

You are considering a new delivery system and wish to test whether delivery times are significantly different, on average than your current system. It is well established that the mean delivery time of the current system is 2.38 days. A test of the new system shows that, with 48 observations, the
As part of a decision regarding a new product launch, you want to test whether or not a large enough percentage (10% or more) of the community would be interested in purchasing it. You will launch the product only if you find convincing evidence of such demand. A survey of 400 randomly selected
Test whether or not the population percentage could reasonably be 20%, based on the observed 18.4% who like your products, from a random sample of 500 consumers.
Do initial public offerings (IPOs) of stock significantly increase in value, on average, in the short term? Test using the data from Table 4.3.7 that show the performance of initial offerings as percent increases from the offer price, with most newly traded companies increasing in value while some
The p-value is 0.0371. What conclusions can you reach and what error might have been made?
At a recent meeting, it was decided to go ahead with the introduction of a new product if “interested consumers would be willing, on average, to pay $20.00 for the product.” A study was conducted, with 315 random interested consumers indicating that they would pay an average of $18.14 for the
Your bakery produces loaves of bread with “1 pound” written on the label. Here are weights of randomly sampled loaves from today’s production: 1.02, 0.97, 0.98, 1.10, 1.00, 1.02, 0.98, 1.03, 1.03, 1.05, 1.02, 1.06 a. Find the 95% confidence interval for the mean weight of all loaves
Your factory’s inventory level was determined at 12 randomly selected times last year, with the following results: 313, 891, 153, 387, 584, 162, 742, 684, 277, 271, 285, 845 a. Find the typical inventory level throughout the whole year, using the standard statistical summary. b.
Some of your advertisements seem to get no reaction, as though they are being ignored by the public. You have arranged for a study to measure the public’s awareness of your brand before and after viewing a TV show that includes the advertisement in question. You wish to see if the ad has a
Part of the assembly line will need adjusting if the consistency of the injected plastic becomes either too viscous or not viscous enough as compared with a value (56.00) your engineers consider reasonable. You will decide to adjust only if you are convinced that the system is “not in control,”
What standard error would you use to test whether a new observation came from the same population as a sample?
Suppose you have an estimator and would like to test whether or not the population mean value equals 0. What do you need in addition to the estimated value?
Suppose you learn that the p-value for a hypothesis test is equal to 0.0217. What can you say about the result of this test?
From a list of the 729 people who went on a cruise, 130 were randomly selected for interview. Of these, 112 said that they were very happy with the accommodations. Find the 95% confidence interval for the population percentage who would have said they were very happy with the accommodations.
Find the one-sided 95% confidence interval for the weight of candy bars after intervention, based on the data in Table 5.5.4, indicating that the population mean weight is no more than some amount. TABLE 5.5.4 Weight (in Ounces) for Two Samples of Candy Bars Before Before After After
Find the 99.9% confidence interval for the weight of candy bars before intervention, based on the data in Table 5.5.4 of Chapter 5. TABLE 5.5.4 Weight (in Ounces) for Two Samples of Candy Bars Before Before After After Intervention Intervention Intervention Intervention 1.62 1.68 1.60 1.69
Find the 95% confidence interval for the amounts that your regular customers spent on your products last month, viewing the data from Table 4.3.1 of Chapter 4 as a random sample of customer orders. TABLE 4.3.1 Last Month's Sales Customer Consolidated, Inc International, Ltd Sales ($000)
A market survey has shown that people will spend an average of $2.34 each for your product next year, based on a sample survey of 400 people. The standard deviation of the sample was $0.72. Find the two-sided 95% confidence interval for next year’s mean expenditure per person in the larger
Table 9.6.2 shows the 2015 performance of stocks recommended by Gene Marcial, whose list was published in Forbes in December 2014. a. Compute the average and briefly describe its meaning. b. Compute the standard deviation and briefly describe its meaning. c. Compute the standard
Based on the following daily percent changes of the S&P 500 stock market index for June 2010 (accessed at http:// finance.Yahoo.com on July 13, 2010), find the 95% confidence interval for the population mean daily change. (This is not, strictly speaking, a random sample from a population.
Comparison shopping is available on the Internet, and this is useful because exactly the same item is available at a variety of prices. Table 9.6.1 shows results from MySimon for prices of the Eureka 4750A Bagged Upright Vacuum at 15 stores. Find the 95% confidence interval for the average price in
Your firm is in the market to hire an experienced vice president of information technology or information systems. If one is chosen at random from the population represented in the preceding problem, complete the following sentence: We are 99% sure that the chosen manager’s salary is at least
A nationwide poll claims that the margin of error is no more than 4.3 percentage points for questions asked of half the sample (at the 95% confidence level). a. Verify this claim in a particular case by computing the critical t value times the standard error of the binomial fraction p for the case
In a sample of 258 individuals selected randomly from a city of 750,339 people, 165 were found to be supportive of a new public works project. Find the 99.9% confidence interval for the support level percentage in the entire city.
A recent survey of 252 customers, selected at random from a database with 12,861 customers, found that 208 are satisfied with the service they are receiving. Find the 99% confidence interval for the percentage satisfied for all customers in the database.
A market survey has shown that people will spend an average of $15.48 each for your product next year, based on a sample survey of 483 people. The standard deviation of the sample was $2.52. Find the two-sided 95% confidence interval for next year’s mean expenditure per person in the larger
Click-through rates were measured for each of 83 mobile advertising campaigns, and showed an average rate of 2.38%, with a standard error of 0.134%. Please note that this is not a binomial situation because we are analyzing 83 percentage numbers and we do not know the size of each campaign. a.
Cost observations provided for 21 production situations have an average of $149.67 and a standard deviation of $38.85. a. Find and interpret the two-sided 95% confidence interval. b. Find the two-sided 99.9% confidence interval. c. Find the one-sided 95% confidence interval that
Main-course taste scores have been recorded for 48 restaurant diners on a scale from 1 to 5. The average score was 4.125, the standard error was 0.1099, and the 95% confidence interval extended from 3.904 to 4.346. Find the margin of error.
Consumer preferences have been observed in a situation for which the standard error is known. Find the critical t value to use for each of the following confidence interval calculations: a. Two-sided 95% confidence. b. Two-sided 99% confidence. c. Two-sided 99.9% confidence. d.
Vaccine responses have been observed for 1,859 people. Find the critical t value to use for each of the following confidence interval calculations: a. Two-sided 95% confidence. b. Two-sided 99% confidence. c. Two-sided 99.9% confidence. d. Two-sided 90% confidence.
Intensities have been measured for eight flashlights. Find the critical t value to use for each of the following confidence interval calculations: a. Two-sided 95% confidence. b. Two-sided 99% confidence. c. Two-sided 99.9% confidence. d. Two-sided 90% confidence
Your quality control department has just analyzed the contents of 20 randomly selected barrels of materials to be used in manufacturing plastic garden equipment. The results found an average of 41.93 gallons of usable material per barrel, with a standard error of 0.040 gallon per barrel. Find the
Your hospital is negotiating with medical insurance providers, who would like to reduce the amount they pay as reimbursement for hospital stays. For a particular procedure, they would like to reduce payment by $300 and have patients go home one day earlier. To see what effect this would have on
Your company prepares and distributes frozen foods. The package claims a net weight of 24.5 oz. A random sample of today’s production was weighed, and the results were summarized as follows: average = 24.41 oz, standard deviation = 0.11 oz, sample size = 5 packages. Find the two-sided 95%
Your agricultural firm is considering the purchase of some farmland, and an indication of the quality of the land will be helpful. A random sample of 62 selected locations planted with corn indicates an average yield of 103.6 bushels per acre, with a standard deviation of 9.4 bushels per acre. Find
Why are critical t values generally larger than 1.960 for a two-sided 95% confidence interval?
Which fact about a normal distribution leads to the factor 2 (or 1.960) in the approximate confidence interval statement?
What does a confidence interval tell you about the population that an estimated value alone does not?
In what important way does statistical inference go beyond summarizing the data?
A survey of 823 randomly selected adults in the United States finds that 63% support current government policies. Find the usual measure that indicates approximately how far this sample percentage is from the value that would have been found if all adults in the United States had been interviewed.
Find the average and the standard error for the weight of candy bars before intervention, based on the data in Table 5.4 of Chapter 5.
Find the average and the standard error for the strength of cotton yarn used in a weaving factory, based on the data in problem 23 of Chapter 4.
Find the average and the standard error for the amounts that your regular customers spent on your products last month, viewing the data from problem 2 of Chapter 4 as a sample of customer orders.
Find the standard error of the average for the following data set representing quality of agricultural produce: 16:7,17:9,23:5,13:8,15:9,15:2,12:9,15:7
Economists often make forecasts of future conditions. Consider the US unemployment rate for June 2015 as predicted in October 2014 as part of a survey of economists, as shown in Table 8.6.4. a. Find the average and the standard deviation. Briefly interpret these values. b. Find the
You have analyzed a project using four scenarios, with the results shown in Table 8.6.1. Suppose you actually have 40 projects just like this one and they pay off independently of one another. Find the probability that your average profit per project will be between $5 million and $6 million.
The population mean is $65 and the population standard deviation is $30. Find the probability that the average of 35 randomly selected transactions is between $55 and $60. You may assume that the population is approximately normally distributed.
A farmer has five identical cornfields, each of which independently produces a normally distributed harvest with a mean of 80,000 bushels and a standard deviation of 15,000 bushels. Find the probability that the average harvest for the five fields will exceed 88,000 bushels.
You have interviewed 369 people out of a population of 30,916 and found that 51.8% expect to vote for the challenger in the upcoming election. Find the standard error of this estimate.
Deposits have a mean of $125 and a standard deviation of $36. Find the standard deviation of the average amount of 12 randomly selected deposits.
You have estimated the inventory value of your competition as $384,000 but later learn that the true inventory value was $416,000. Find the estimation error.
You have eight machines operating independently. The mean production rate for each machine is 20.3 tons/day, and the standard deviation is 1.4 tons/day. Approximately how much uncertainty is there in the average daily production for the eight machines? Please report the usual summary measure.
The population mean productivity is 35, the population standard deviation is 10, and the sample size is 15. Find the standard deviation of the total amount represented by a random sample.
The mean account balance is $500 and the standard deviation is $120 for a large population of bank accounts. Find the standard deviation of the average balance of groups of eight accounts (chosen independently of one another and with equal probabilities of selection).
Draw a random sample of eight invoices from a population of 500 overdue billings, starting with row 17, column 5 of the table of random digits.
Draw a random sample of five contracts from a population of 362 recent contracts with cost overruns, starting with row 13, column 5 of the table of random digits.
Draw a random sample of four firms from a population of 86 suppliers, starting with row 30, column 4 of the table of random digits.
Draw a random sample of three account numbers from a population of 681 accounts receivable documents, starting with row 6, column 2 of the table of random digits.
Select a random sample of four without replacement from the following metal products corporations: Gillette, Crown Cork & Seal, MASCO, Tyco Laboratories, Illinois Tool Works, McDermott, Ball, Stanley Works, Harsco, Hillenbrand Industries, Newell, Snap-on Tools, Danaher, Silgan, Robertson-Ceco,
Select a random sample of three without replacement from the following (very small) population of firms: IBM, GM, Ford, Shell, HP, Boeing, and ITT. Use the following sequence of random digits: 5887053671352339.
Which of the following samples is likely to be the most representative of the population of all employees at IBM? a. The 10 oldest and most experienced researchers at the Thomas J. Watson Research Center. b. A random sample of 10 computer repair specialists. c. The 10 employees
Which of the following samples is likely to be the most representative of the population of all registered voters in the United States? a. A sample of 200 people at a Denver shopping mall. b. A sample of 200 of your friends and their friends. c. A sample of 200 people, chosen by
What do the standard errors Sx and Sp indicate for a binomial situation?
a. What is a statistic? b. What is the parameter?
Customers arrive at random times, with an exponential distribution for the time between arrivals. Currently, the mean time between customers is 6.34 minutes. a. Since the last customer arrived, 3 minutes have gone by. Find the meantime until the next customer arrives. b. Since the last
Suppose 17% of the items in a large warehouse are defective. You have chosen a random sample of 350 items to examine in detail. Find the probability that more than 20% of the sample is defective.
Although you do not know the exact total amount of payments you will receive next month, based on past experience you believe it will be approximately $2,500 more or less than $13,000, and will follow a normal distribution. Find the probability that you will receive between $10,000 and $15,000 next
Assume that electronic microchip operating speeds are normally distributed with a mean of 2.5 GHz and a standard deviation of 0.4 GHz. What percentage of your production would you expect to be “Superchips” with operating speeds of 3 GHz or more?
You are a farmer about to harvest your crop. To describe the uncertainty in the size of the harvest, you feel that it may be described as a normal distribution with a mean value of 80,000 bushels and a standard deviation of 2,500 bushels. Find the probability that your harvest will exceed 84,000
The amount of ore (in tons) in a segment of a mine is assumed to follow a normal distribution with mean 185 and standard deviation 40. Find the probability that the amount of ore is less than 175 tons.
Based on recent experience, you expect this Saturday’s total receipts to have a mean of $2,353.25 and a standard deviation of $291.63 and to be normally distributed. a. Find the probability of a typical Saturday, defined as total receipts between $2,000 and $2,500. b. Find the
The quality control section of a purchasing contract for valves specifies that the diameter must be between 2.53 and 2.57 cm. Assume that the production equipment is set so that the mean diameter is 2.56 cm and the standard deviation is 0.01 cm. What percent of valves produced, over the long run,
Find the probability that you will see moderate improvement in productivity, meaning an increase in productivity between 6 and 13. You may assume that the productivity increase follows a normal distribution with a mean of 10 and a standard deviation of 7.
You are planning to make sales calls at eight firms today. As a rough approximation, you figure that each call has a 20% chance of resulting in a sale and that firms make their buying decisions without consulting each other. Find the probability of having a really terrible day with no sales at all.
You have just performed a survey interviewing 358 randomly selected people. You found that 94 of them are interested in possibly purchasing a new cable TV service. How much uncertainty is there in this number “94” as compared to the average number you would expect to find in such a survey? (You
An election coming up next week promises to be very close. In fact, assume that 50% are in favor and 50% are against. Suppose you conduct a poll of 791 randomly selected likely voters. Approximately how different will the percent in favor (from the poll) be from the 50% in the population you are
know that one of your customers has been having trouble with the recession and may not be able to make the loan payment that is due next week. You believe there is a 60% chance that the payment of $50,000 will be made in full, a 30% chance that only half will be paid, and a 10% chance that no
A new project has an uncertain cash flow. A group meeting has resulted in a consensus that a reasonable way to view the possible risks and rewards is to say that the project will pay $50,000 with probability 0.2, will pay $100,000 with probability 0.3, will pay $200,000 with probability 0.4, and
On a given day, assume that there is a 30% chance you will receive no orders, a 50% chance you will receive one order, a 15% chance of two orders, and a 5% chance of three orders. Find the expected number of orders and the variability in the number of orders.
An investment will pay $105 with probability 0.7, and $125 with probability 0.3. Find the risk (as measured by standard deviation) for this investment.
a. How do you tell if a random variable has a binomial distribution? b. What is a binomial proportion? c. What are n, π, X, and p?
You are in the process of assessing your firm’s online marketing strategy, and would like to know whether visitors to your Website who arrive from a search engine ad (after searching for your firm’s products) are more or are less likely to make a purchase than others. Focusing on all recent
As part of an assessment of the role of organized activities for your user base, you have compiled the following facts regarding attendance at the most recent User Conference and subsequent software license renewal. The universe you are studying consists of all users with an active license at the
Do studies have an impact on future activities in society? A study of New Jersey adults found that those who studied civics in school were more likely to vote in a recent election.17 Specifically, 55.0% studied civics in school. Of those who studied civics, 90% voted. Among those who did not study
You are a contestant on a TV game show with five doors. There is just one prize behind one door, randomly selected. After you choose, the hosts deliberately open three doors (other than your choice) that do not have the prize. You have the opportunity to switch doors from your original choice to
The probability of getting a patent is 0.6. If you get the patent, the conditional probability of being profitable is 0.9. However, given that you do not get the patent, the conditional probability of being profitable is only 0.3. Find the probability of being profitable.
You feel that the schedule is reasonable provided the new manager can be hired in time, but the situation is risky regardless. You figure there is a 70% chance of hiring the new manager in time. If the new manager is hired in time, the chances for success are 80%; however, if the new manager cannot
You have determined that 2.1% of the CDs that your factory manufactures are defective due to a problem with materials and that 1.3% are defective due to human error. Assuming that these are independent events, find the probability that a CD will have at least one of these defects.
Your production line has an automatic scanner to detect defects. In recent production, 2% of items have been defective. Given that an item is defective, the scanner has a 90% chance of identifying it as defective. Of the nondefective items, the scanner has a 90% chance of identifying it correctly
The probability that the project succeeds in New York is 0.6, the probability that it succeeds in Chicago is 0.7, and the probability that it succeeds in both markets is 0.55. Find the conditional probability that it succeeds in Chicago given that it succeeds in New York.
Suppose 35.0% of employees are staff scientists, 26.0% are senior employees, and 9.1% are both. Are “staff scientist” and “senior employee” independent events?
You just learned good news: A prototype of the new product was completed ahead of schedule and it works better than expected. Would you expect “the conditional probability that this product will be successful given the good news” to be larger than, smaller than, or equal to the (unconditional)
Your firm is interested in learning more about customers’ purchasing patterns on its Web site and how they relate to the frequency of online site visits. The probability that a customer’s visit will result in a purchase is 0.35. The probability that a customer has been to the site within the
The probability of getting a big order currently under negotiation is 0.32. The probability of losing money this quarter is 0.54. a. Assume that these are mutually exclusive events. Find the probability of getting the order or losing money this quarter. b. Again assume that these are
You are responsible for a staff of 32 out of the 118 workers in a rug-weaving factory. Next Monday a representative will be chosen from these 118 workers. Assume that the representative is chosen at random, without regard to whether he or she works for you. a. What is the probability that one
Of the 925 tires your factory just produced, 17 are defective. a. Find the probability that a randomly selected tire is defective. b. Find the probability that a randomly selected tire is not defective. c. What kind of probability numbers are these?
What is a joint probability table?
What are mutually exclusive events?
1. Are Kellerman’s calculations correct? These are the first items to verify. 2. Take a close look at the data using appropriate statistical methods. 3. Are Kellerman’s conclusions correct? If so, why do you think so? If not, why not and what should be done instead? You and your

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Practical Business Statistics 7th Edition Andrew Siegel - Solutions

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