The tourism board of a large metropolitan area is seeking ways to promote tourism. They have identified five factors (A, B, C, D, and E) that they feel have an impact on tourist satisfaction. Factor C has four levels, and each of the other four factors has two levels. Show an experimental design, using an orthogonal array, that could estimate the factor effects.
> A fast-food restaurant in an urban area experiences a higher traffic rate during the early morning and lunch hours. In order to conduct a customer satisfaction survey, discuss possible sampling procedures.
> A limousine service catering to a large metropolitan area has found that the time for a trip (from dispatch to return) is exponentially distributed with a mean of 30 minutes. (a) What is the probability that a trip will take more than an hour? (b) If a l
> The time to repair an equipment is known to be exponentially distributed with a mean of 45 min. (a) What is the probability of the machine being repaired within half an hour? (b) If the machine breaks down at 3 P.M. and a repairman is available immediate
> A component is known to have an exponential time-to-failure distribution with a mean life of 10,000 hours. (a) What is the probability of the component lasting at least 8000 hours? (b) If the component is in operation at 9000 hours, what is the probabili
> A company has been able to restrict the use of electrical power through energy conservation measures. The monthly use is known to be normal with a mean of 60,000 kWh (kilowatt-hour) and a standard deviation of 400 kWh. (a) What is the probability that th
> The specifications for the thickness of nonferrous washers are 1.0±0.04 mm. From process data, the distribution of the washer thickness is estimated to be normal with a mean of 0.98 mm and a standard deviation of 0.02 mm. The unit cost of rework is $0.10
> The breaking strength of a cable is known to be normally distributed with a mean of 4000 kg and a standard deviation of 25 kg. The manufacturer prefers that at least 95%of its product meet a strength requirement of 4050 kg. Is this requirement being met?
> The outside diameter of a part used in a gear assembly is known to be normally distributed with a mean of 40 mm and standard deviation of 2.5 mm. The specifications on the diameter are (36, 45), which means that part diameters between 36 and 45 mm are co
> The number of bank failures per year among those insured by the Federal Deposit Insurance Company has a mean of 7.0. The failures occur independently. What is the probability that: (a) there will be at least 4 failures in the coming year? (b) there will
> In an auto body shop, it is known that the average number of paint blemishes per car is 3. If 2 cars are randomly chosen for inspection, what is the probability that: (a) the first car has no more than 2 blemishes? (b) each of the cars has no more than 2
> The enter for Medicare and Medicaid Services (CMS) reimburses health care facilities at a fixed rate for patients of a certain diagnosis-related group (DRG). The facility must also demonstrate an acceptable level of performance at the aggregate level. Fo
> Explain type I and type II errors in the context of sampling from customers’ accounts to identify billing errors in a large retail store. What are the associated costs of these two types of errors?
> An urban health care facility is interested in providing quality care at an affordable price to all patients. On average, the facility serves 500 patients monthly, with the average net contribution to profit being $400 per patient. Recently, a quality im
> Consider Exercise 1-22. Suppose that market share is strongly influenced by the level of quality, with the revenue function given by 90q2. What is the net profit function? What is the minimum desirable quality level to break even? Data from Exercise 1-2
> Suppose that the prevention cost function is as given in Exercise 1-21. However, the unit appraisal cost is $2, with the cost function being linear in 1 q, implying a decrease in appraisal costs as quality improves. Further, the rework and external failu
> Suppose that the prevention and appraisal cost functions are given by Cp= 50q2 and Ca=10q, respectively, where q represents the degree of quality level (0< q< 1). The cost of reworking a unit is $5, and the cost of a customer obtaining a nonconforming pr
> In the production of a part for a printer, four sequential operations are involved. Unit processing costs for the operations are $10, $6, $15, and $20, respectively. The first pass yields for each operation are 0.95, 0.90, 0.95, and 0.85, respectively. U
> The following data (in $/m^3) were obtained from a company that makes insulation for commercial buildings: direct labor, 20; direct materials, 30; indirect labor and materials, 30% of direct labor; fixed expenses, 25; administrative costs, 25; selling co
> A pharmaceutical company has obtained the following cost information (per 1000 tablets) based on the production of a drug in the past year: material, $150; direct labor, $100; energy, $50; overhead, 40% of direct labor and material. Presently, the proces
> Consider the hardware company in Exercise 1-15. The company is contemplating outsourcing of its complex monitor M2. Assume that all other information remains as given in Exercise 1-15. Information from Exercise 1-15: An assemble-to-order hardware company
> The settling of unwanted material in a mold is causing some defects in the output. Based on recent data, it is estimated that 5% of the output has one or more defects. In spot checking some parts, an inspector randomly selects two parts. Find the probabi
> An assemble-to-order hardware company has two types of central processing units (CPUs), C1 and C2, and two types of display monitors, M1 and M2. Unit C2 is slightly more complex than C1, as is M2 compared to M1. The annual production volume and direct co
> Explain the relationship between a type I error, power, degree of difference that one wishes to detect in a parameter value, and sample size. How can a type I error be reduced and the power be increased for a given difference in the parameter?
> Based on historical data, it is estimated that 12% of new products will obtain a profitable market share. However, if two products are newly introduced in the same year, there is only a 5% chance of both products becoming profitable. A company is plannin
> An automobile manufacturing company is attempting to cope with rising health care costs of its employees. It offers three types of plans. Based on a random sample of 200 employees selected last year, Table 5-11 shows the number who selected each plan. Th
> Percentage investment in new-product development is monitored for a pharmaceutical company by quarter. The observations are listed row wise: (a) Can we conclude that the sequence of investment percentages is random? Use α= 0.05. (b) Is ther
> The pH values of a dye for 30 samples taken consecutively over time are listed row wise: (a) Can we conclude that the sequence of pH values over time is non-random? Use α = 0.05. (b) Assume that dyes are produced in batches, with 10 random
> Using the call waiting time of customer data in Exercise 5-9, construct a stem-and-leaf plot. Construct a box plot and comment on the distribution. Are there any outliers? Construct a 95% confidence interval for the median. Data from Exercise 5-9: A ran
> A random sample of 50 observations on the waiting time (in seconds) of customers before speaking to a representative at a call center is as follows: (a) Construct a histogram and comment on the process. (b) What assumptions are necessary to test if the m
> A remote control unit has 40 components in series. The reliability of each component is 0.9994. What is the reliability of the remote control unit? If a redesign has 25 components in series, what is the reliability of the unit?
> A retail company has information on the time taken (in days) to fulfil an order, the value of the order (in $10,000), the number of different types of products in the order, and the store location. The data are shown in Table 13-8. (a) Find a simple regr
> Refer to the data in Table 13-9 on diabetic patients and the development of retinopathy. (a) Develop a regression model to predict the probability of development of retinopathy based on years of diabetes and gender of person. Is the model significant at
> Table 13-9 shows data on diabetic patients and the development of retinopathy. The gender of the person, number of years that the person has been diagnosed with diabetes (labelled as Years), and whether the person has developed retinopathy (Y = Yes; N =
> A financial institution is contemplating the offering of three different types of savings accounts. Its elects 100 customers randomly and obtains a response on which account each person would select. What statistical test would you use to determine if cu
> Refer to the data in Table 13-6 on obesity, gender, and occurrence of a heart attack. (a) Develop a regression model to predict the chance of a heart attack based on weight. Interpret the model coefficients. (b) Is the model significant using Î&plu
> Refer to the data in Table 13-8 on order fulfilment time. (a) You believe that there are differences, in general, in the value of orders by location of the store. Consequently, its impact on order fulfilment time may be influenced as such. Find the model
> Refer to the data in Table 13-8 on order fulfilment time. (a) You decide to develop a regression model using order value, number of products, and location of the retailer as predictors. Find the model equation. Is it significant at α =0.05?
> Refer to the data in Table 13-8 on order fulfilment time. (a) You decide to develop a regression model using order value and the number of products in the order as predictors. Find the model equation. Is it significant at α =0.05? (b) Find
> Refer to Exercise 13-9 and the corresponding data shown in Table 13-8. (a) Based on a scatterplot of order fulfillment time versus order value, you decide to fit a quadratic model in order value. What is the model equation? (b) What are values of R2 and
> Refer to Exercise 13-9 and the regression model of time to fulfil an order based on order value. Data from Exercise 13-9: A retail company has information on the time taken (in days) to fulfil an order, the value of the order (in $10,000), the number of
> Consider Exercise 12-50. Four factors (A, B, C, and D), each at three levels, are controlled in an experiment using an L9 orthogonal array. The output quality is classified as acceptable or unacceptable; unacceptable includes both the second-class and re
> In a textile processing plant the quality of the output fabric is believed to be influenced by four factors (A, B, C, and D), each of which can be controlled at three levels. The fabric is classified into three categories: acceptable, second-class, or re
> Consider Exercise 12-48. The design factors are A, B, C, and D, each at three levels. These are assigned to an orthogonal array (inner array) with the factors A, B, C, and D assigned to columns 1, 2, 3, and 4, respectively. Suppose that, in addition to t
> In a food processing plant, four design parameters, A, B, C, and D, each at three levels, have been identified as having an effect on the moisture content in packaged meat. Three noise factors, E, F, and G, each at two levels, are also to be investigated
> Data from a survey of customers are on an ordinal scale (1–7) regarding satisfaction with the services provided in a bank by three tellers. If we wish to determine if the degree of customer satisfaction is independent of the teller, what statistical test
> A travel agency is attempting to enter a market where several competitors currently exist. What are the various customer needs that they should address? How will quality be measured? As the company strives to improve its market share, discuss the impact
> Consider Exercise 12-46. With the assignment of factors, A, B, C, and D to columns 1, 2, 3, and 4, respectively, of an L9 orthogonal array, the output is as follows for another replication of the nine experiments: Determine the main effects. Plot the ave
> In a drilling operation, four factors (A, B, C, and D), each at three levels, are thought to be of importance in influencing the volume of crude oil pumped. Using an L9 orthogonal array, the factors A, B, C, and D are assigned to columns 1, 2, 3, and 4,
> A city library has established three factors (A, B, and C), each at three levels, that influence the satisfaction of their patrons. The library governance committee also believes that the interaction B × C is important. Using an orthogonal array, set up
> A baseball team manager believes that five factors (A, B, C, D, and E), each at two levels, are significant in affecting runs batted in. The manager believes that the interactions B× C and B × E are important. Show an experimental design using an orthogo
> The Environmental Protection Agency has identified four factors (A, B, C, and D), each at two levels, that are significant in their effect on the air pollution level at a photographic film production facility. The agency also feels that the interaction e
> Refer to Exercise 12-40. The restaurant is thinking of hiring more personnel to cut down the service time. However, the additional cost of increasing personnel is estimated to be $0.50 per customer. The results of sampling with the added personnel yield
> A restaurant believes that two of the most important factors that help it attract and retain customers are the price of the item and the time taken to serve the customer. Based on the price for similar items in other neighboring restaurants, it is estima
> Refer to Exercise 12-36. Suppose the manufacturer has the ability to centre the process such that the average thickness of the coating is at 0.005 mm, which is the target value. In doing so, the manufacturer estimates that the standard deviation of the p
> Refer to Exercise 12-36. Suppose that the manufacturer can rework the thickness prior to shipping the product at a cost of $2.00 per reel. What should the manufacturer’s tolerance be? Data from Exercise 12-36: A manufacturer of magnetic tapes is interes
> A county wishes to estimate the average income of people, where it is known that income levels vary quite a bit among the residents in sections of the county. What type of sampling scheme should be used?
> Refer to Exercise 12-36. The manufacturer is considering adopting a new process to reduce the variability in the thickness of coating. It is estimated that the additional cost for this improvement is $0.03 per linear meter. The annual production is 10,00
> A manufacturer of magnetic tapes is interested in reducing the variability of the thickness of the coating on the tape. It is estimated that the loss to the consumer is $10 per reel if the thickness exceeds 0.005 ±0.0004 mm. Each reel has 200 m of tape.
> Refer to Exercise 12-30. Factor A is the concentration of corn extract, factor B is the concentration of an ethylene-based compound, and factor C is the distillation temperature. Each factor will be controlled at two levels. Suppose the experimenter runs
> In a 2^5-2 fractional factorial experiment, using CDE and AB as the generators, find the treatment combinations. Find the aliases of the contrasts.
> Consider a 2^4 factorial experiment. Using BC as the defining contrast, find the treatment combinations in a 2^4–1 fractional factorial experiment. Find the aliases of the contrasts. How would it be possible to estimate the effect of the contrast BC? If
> In Exercise 12-31, use AB as the confounding factor to divide the experiment into two blocks. How would you estimate the effect of factor A? Data from Exercise 12-31: Consider a 2^4 factorial experiment. Set up a table of the coefficients for orthogonal
> Consider a 2^4 factorial experiment. Set up a table of the coefficients for orthogonal contrasts similar to Table 12-25. Write down the contrasts for estimating the main effects and the two-factor interactions. If the four-way interaction effect ABCD is
> In the search for a lower-pollution synthetic fuel, researchers are experimenting with three different factors, each controlled at two levels, for the processing of such a fuel. Factor A is the concentration of corn extract at 5% and 10%, factor B is the
> Write out the treatment combinations for a 2^4 factorial experiment.
> Refer to Exercise 12-20. Consider the following three contrasts: (1) difference between the sum of the reduction in blood sugar levels using diet types 1 and 3 from that using diet types 2 and 4; (2) difference between the sum of the reduction in blood s
> Explain some specific parametric tests that require the distributional assumption of normality. What do you do if the assumption is not satisfied?
> Refer to Exercise 12-19. Consider the following two contrasts of totals: (1) difference between the totals for training programs 1 and 3; (2) difference between the totals for the sum of training programs 1 and 3 and twice that of training program 2. (a)
> Refer to Exercise 12-19. Find a 90% confidence interval for the difference in the mean effectiveness of program 1 and the average of that using programs 2 and 3. Data from Exercise 12-19: Three training programs are being considered for auditors in an a
> Refer to Exercise 12-18. (a) Is there a difference in the mean number of passengers bumped using software packages 1 and 2 from that using software packages 3 and 4? Test at the 10% level of significance. (b) Find a 95% confidence interval for the contra
> Refer to Exercise 12-17. (a) Is there a difference between the mean degree of lateness of company 3 and that of the averages of companies 1 and 2? Test at the 5% level of significance. (b) Find a 90% confidence interval for the contrast defined in part (
> Consider Example 12-4 concerning the efficiency of synthetic fuel for which the factors are an additive and a catalyst. The original data are given in Table 12-19. The experiment is conducted using only five randomly chosen automobiles (A, B, C, D, and E
> Two controllable factors, temperature and pressure, are each kept at three levels to determine their impact on the ductility of an alloy being produced. The temperature levels are 150, 250, and 300 °C, respectively. Pressure is controlled at 5
> A consulting firm wishes to evaluate the performance of four software packages (A, B, C, and D) as measured by the computational time. The experimenter wishes to control for two variables: the problem type and the operating system configuration used. Fou
> A doctor is contemplating four types of diet to reduce the blood sugar levels of patients. Because of differences in the metabolism of patients, the doctor categorizes the patients into five age groups. From each age group, four patients are selected and
> Three training programs are being considered for auditors in an accounting firm. The success of the training programs is measured on a rating scale from 0 to 100, with higher values indicating a desirable program. The company has categorized its auditors
> An airline is interested in selecting a software package for its reservation system. Even though the company would like to maximize use of its available seats, it prefers to bump as few passengers as possible. It has four software packages to choose from
> A 95% confidence interval for the mean thickness of a part in millimetres is (10.2, 12.9). Interpret this interval.
> A large retail company has to deliver its goods to distributors throughout the country. It has been offered trial-run services by three transportation companies. To test the efficiency of these three companies, it randomly assigns its outgoing product sh
> Refer to Exercise 11-8 concerning the redesigned remote control unit with 25 components in series. If it is desired that the remote unit has a reliability of 0.996 for 3000 hours of operation, what should the failure rate be for each component? What shou
> Refer to Exercise 11-31. Test the null hypothesis of equality of the survival functions of the two groups using a level of significance of 0.05. Data from Exercise 11-31: Two groups of samples of patients were randomly selected from a county. The first
> Two groups of samples of patients were randomly selected from a county. The first group (Group 1) had no history of a chronic disease while the second group (Group 2) had a positive history. The selected patients were observed for a period of 15 years. S
> Refer to Exercise 11-29. If failed items are not replaced during the test, determine the plan using Handbook H-108. Data from Exercise 11-29: In a time-terminated life testing plan, it is desired to reject lots with a mean life of 1500 hours with a prob
> In a time-terminated life testing plan, it is desired to reject lots with a mean life of 1500 hours with a probability of 0.95 and reject lots with a mean life of 7500 hours with a probability of 0.10. The test is to be terminated by 2500 hours. Items th
> Refer to Exercise 11-27. Find the appropriate plan using Handbook H-108 if failed items are not replaced during the test. Data from Exercise 11-27: A time-terminated life testing plan is desired that will accept lots with a mean life of 6000 hours with
> A time-terminated life testing plan is desired that will accept lots with a mean life of 6000 hours with a probability of 0.99 and will accept lots with a mean life of 2000 hours with a probability of 0.10. The test should be terminated by 1200 hours. It
> Refer to Exercise 11-25. If failed items are replaced with similar items, determine a life testing plan using Handbook H-108. Data from Exercise 11-25: A time-terminated life testing plan is to be found that will reject lots that have a mean life of 140
> A time-terminated life testing plan is to be found that will reject lots that have a mean life of 1400 hours with a probability of 0.05. The rejection number is 7, with a sample size of 35. Determine the plan using Handbook H-108 if the time to failure i
> Distinguish between a hypergeometric and a binomial random variable.
> Refer to Exercise 11-23. Suppose that items that fail during the test are immediately replaced with similar items. Determine the life testing plan using Handbook H-108. Data from Exercise 11-23: A time-terminated life testing plan is to be found that wi
> A time-terminated life testing plan is to be found that will reject lots with a mean life of 1500 hours with a probability 0.05 and accept lots with a mean life of 600 hours with a probability of 0.10. Items that fail during the test are not replaced. De
> A life testing plan is to be terminated after the third failure. It should accept a lot that has an acceptable mean life of 600 hours with a probability of 0.99. Failed items are not replaced during the test. A sample of eight items is chosen, and three
> Refer to Exercise 11-20. Assume that failed items are immediately replaced during the test. Using Handbook H-108, what is your recommendation on the lot? Data from Exercise 11-20: A life testing plan is to be terminated after the eighth failure. It shou
> A life testing plan isto be terminated after the eighth failure. It should reject a lot that has an acceptable mean life of 900 hours with a probability of 0.10. Items that fail during the test are not replaced. A sample of 15 items is placed on test wit
> A sample of 25 relays is chosen for life testing. The time to failure of a relay is exponentially distributed. The test is terminated after 800 hours, with five failures being observed at times 610, 630, 680, 700, and 720 hours. Failed items are not repl
> Refer to Exercise 11-17. Assume that each failed item is replaced with an identical unit. Estimate the mean time to failure and the failure rate. Find a 90% confidence interval for the mean time to failure. Data from Exercise 11-17: A sample of 20 diode
> A sample of 20 diodes is chosen for life testing. The time to failure of the diodes is exponentially distributed. The test is terminated after six failures, with no replacement of the failed items. The failure times (in hours) of the six diodes are 530,
> Construct the OC curve for the life testing plan n= 6, T =900 hours, c =3. For a producer’s risk of 0.05, what is the associated quality of batches as indicated by their mean life? For a consumer’s risk of 0.10, what is the associated quality level of ba
> Refer to Exercise 11-13 and the system shown in Figure 11-14. Suppose that component B is a standby component. Find the reliability of the system after 1000 hours. What is the mean time to failure? Data from Exercise 11-13: Consider the seven-component
> State the null and alternative hypotheses in the following situations by defining the parameters used. Also, state any assumptions that you need to make to conduct the test: (a) The Postal Service wishes to prove that the mean delivery time for packages
