Questions and Answers of Principles Of Operations

Define the following terms:a. Flow shop.b. Job shop.c. Sequential versus parallel processing.d. Makespan.e. Tardiness.
In Problem 1, why are (a) and (c) conflicting objectives, and why are (b) and (d)conflicting objectives?
Discuss each of the following objectives listed and the relationship each has with job shop performance.a. Reduce WIP inventory.b. Provide a high level of customer service.c. Reduce worker idle
Along the lines described in Problem 52, construct a spreadsheet for finding the least unit cost lot-sizing rule.a. Solve both parts (a) and (b) of Problem 52.b. Which method, least unit cost or
This identifies the first forecast horizon.Nowreplace entries in column 2 with zeros and input requirements starting at the current period. Continue until the next forecast horizon is identified.
Work out the logic that gives C( j) in column 3.Onewould use such a spreadsheet in the followingway: Input requirements period by period until an increase is observed in column
Develop a spreadsheet template for finding Silver–Meal solutions for general lotsizing problems. Store the holding and setup cost parameters in separate cell locations so that they can be inputted
The campus store at a large Midwestern university sells writing tablets to students, faculty, and staff. They sell more tablets near exam time. During a typical 10-week quarter, the pattern of sales
The POQ would call for setting the lot size equal to three periods of demand. For the example in Section 8.2, the resulting planned order release would be 116, 0, 0, 150, 0, 0, 135, 0, 0, 38.a.
A popular heuristic lot-sizing method is known as period order quantity (POQ). The method requires determining the average number of periods spanned by the EOQ and choosing the lot size to equal this
A component used in a manufacturing facility is ordered from an outside supplier.Because the component is used in a variety of end products, the demand is high. Estimated demand (in thousands) over
Two end products, EP1 and EP2, are produced in the Raleigh, North Carolina, plant of a large manufacturer of furniture products located in the Southeast. The product structure diagrams for these
Below the net predicted demand for trumpets should be the calculations for the valve casing assembly, and below that the calculations for the valves. For each component, include rows for the
Develop a spreadsheet that reproduces the calculations for Example 8.1. As in the example, the spreadsheet should include the net predicted demand for trumpets. The columns should correspond to weeks
In this chapter, we assumed that the “time bucket” was one week. This implies that forecasts are reevaluated and the MRP system rerun on a weekly basis.a. Discuss the potential advantages of
Vivian Lowe is planning a surprise party for her husband’s 50th birthday. She has decided to serve shish kabob. The recipe that she is using calls for two pineapple chunks for each shrimp. She
Work-in-process (WIP) inventory is a term that refers to the inventory of components and subassemblies in a manufacturing process. Assuming lot-for-lot scheduling at all levels, theoretically the WIP
Solve Problem 42 using part period balancing and least unit cost. Compare the costs of the resulting solutions to the cost of the solution obtained by using the Silver–Meal heuristic.
Suppose that the buttons used in the calculators cost $0.02 each and the company estimates a fixed cost of $12 for placing and receiving orders of the buttons from an outside supplier. Assume that
Consider the example of the CalcIt Company for Problem
CalcIt produces a line of inexpensive pocket calculators. One model, IT53, is a solarpowered scientific model with a liquid crystal display (LCD). The calculator is pictured in Figure 8–11.Each
Discuss the advantages and disadvantages of each of the following features of just-in-time:a. Small lot sizes.b. Integrated purchasing and inventory control.c. Kanban information system.
Explain how the dual-card kanban system operates.
What is SMED? In what way can die-changing operations be reduced by orders of magnitude? Why is it an advantage to do so?
A regional manufacturer of table lamps plans on using a manual kanban information system. On average the firm produces 1,200 lamps monthly. Production lead time is 18 days, and the firm plans to have
What is the difference between a just-in-time system and a kanban system? Can just-in-time be implemented without kanban?
Discuss the concepts of push versus pull and how they relate to just-in-time.
Define the terms rolling horizons and system nervousness in the context of MRP systems.
Planned order releases (POR) for three components, A, B, and C, are given below.Suppose that the yields for these components are respectively 84 percent, 92 percent, and 70 percent. Assuming
For what reason is the capacitated lot-sizing method discussed in Section 8.5 not adequate for solving the overall capacity problem?
Discuss the advantages and disadvantages of including safety stock in MRP lot-sizing calculations. Do you think that a production control manager would be reluctant to build to safety stock if he or
MRP systems have been used with varying degrees of success. Describe under what circumstances MRP might be successful and under what circumstances it would not be successful.
The method of rescheduling the production of a lot to one or more prior periods if the increase in the holding cost is less than the cost of a setup also can be used when no capacity constraints
a. Solve Problem 17 assuming the following production capacities:Week 1 2 3 4 5 6 Capacity 600 600 600 400 200 200b. On a percentage basis, how much larger are the total holding and setup costs in
Solve Problem 14 assuming a maximum order size of 20 per month.
Consider the example presented in Section 8.2 of scheduling the production of the valve casing assembly.a. Suppose that the production capacity in any week is 100 valve casings. Using the algorithm
For the example presented in Problem 6, assume that the setup cost for both components A and B is $100 and that the holding costs are respectively $0.15 and$0.25 per component per week. Using the
Consider the example of Noname Computer Company presented in Problem 4.Suppose that the setup cost for the production of the motherboards is $180 and the holding cost is h $0.40 per motherboard per
If we were to solve Example 8.6 using the Wagner–Whitin algorithm (described in Appendix 8–A), we would obtain (154, 0, 0, 0, 0, 171, 0, 0, 114, 0) as the planned order release for the valve
Solve Problem 17 using theWagner–Whitin algorithm. (Refer to Appendix 8–A.)
a. Based on the results of Problem 20, suggest an approximate lot-sizing technique.Under what circumstances would you expect this method to give good results?b. Use this method to solve Example 8A.2
A small manufacturing firm that produces a line of office furniture requires casters at a fairly constant rate of 75 per week. The MRP system assumes a six-week planning horizon. Assume that it costs
Find the optimal production schedule. (Hint: Modify the first and the last period’s demands to account for starting and ending inventories.)
Anticipated demands for a five-period planning horizon are 14, 3, 0, 26, 15.Current starting inventory is four units, and the inventory manager would like to have eight units on hand at the end of
Anticipated demands for a four-period planning horizon are 23, 86, 40, and 12.The setup cost is $300 and the holding cost is h $3 per unit per period.a. Enumerate all the exact requirements
The time-phased net requirements for the base assembly in a table lamp over the next six weeks are Week 1 2 3 4 5 6 Requirements 335 200 140 440 300 200 The setup cost for the construction of the
Discuss the advantages and disadvantages of the following lot-sizing methods in the context of an MRP scheduling system: lot for lot, EOQ, Silver–Meal, least unit cost, and part period balancing.
For the counterexample (Example 6.3), which shows that the Silver–Meal heuristic may give a suboptimal solution, do either the least unit cost or the part period balancing heuristics give the
Assume a holding cost of $1 per period and a setup cost of $40. Determine the order policy for this item based ona. Silver–Meal.b. Least unit cost.c. Part period balancing.d. Which lot-sizing
Current inventory of this item is 4, and ending inventory should be
A single inventory item is ordered from an outside supplier. The anticipated demand for this item over the next 12 months is 6, 12, 4, 8, 15, 25, 20, 5, 10, 20, 5,
The problem of lot sizing for the valve casing assembly described for Harmon Music Company in Section 8.2 was solved using the EOQ formula. Determine the lot sizing for the 10 periods using the
a. Discuss why the EOQ formula may give poor results for determining planned order releases.b. If the forecasted demand for the end item is the same each period, will the EOQ formula result in
a. Determine the planned order release for the motherboards in Problem 4 assuming that one uses the EOQ formula to schedule production. Use K $180 and h 0.40.b. Using the results from part (a),
Perform the MRP calculations for the valves in the example of this section, using the gross requirements schedule that results from EOQ lot sizing for the valve casing assemblies. Use K $150 and h
An end item has the product structure diagram given in Figure 8–7.a. Write the product structure diagram as an indented bill-of-materials list.b. Suppose that the MPS for the end item is Week 30 31
One of the inputs to the MRP system is the forecast of demand for the end item over the planning horizon. From the point of view of production, what advantages are there to a forecasting system that
What alternatives are there to lot-for-lot scheduling at each level? Discuss the potential advantages and disadvantages of other lot-sizing techniques.
Consider the product structure diagram given in Figure 8–3. Assume that the MPS for the end item for weeks 10 through 17 is Week 10 11 12 13 14 15 16 17 Net requirements 100 100 40 40 100 200 200
For Problem 4, suppose that Noname has 23,000 DRAM chips in inventory. It anticipates receiving a lot of 3,000 chips in week 3 from another firm that has gone out of business.At the current time,
The starting inventory of assembled computers in week 6 will be 75, and the production manager anticipates returns of 30 in week 8 and 10 in week 10.a. Determine the MPS for the computers.b.
The Noname Computer Company builds a computer designated model ICU2. It imports the motherboard of the computer from Taiwan, but the company inserts the sockets for the chips and boards in its plant
For the example of Harmon Music presented in this section, determine the planned order release for the slide assemblies. Assume lot-for-lot scheduling.
What information is contained in a product structure diagram?
The inventory control models discussed in Chapters 4 and 5 are often labeled independent demand models and MRP is often labeled a dependent demand system. What do the terms independent and dependent
A local café has a single cash register, with a single assistant to work it, and three servers working to fill the customer orders. Customers arrive with exponential interarrival time an average of
Cars travelling to the George Washington Bridge from New Jersey to New York City must pay a toll. About 38 percent of the commuters use E-ZPass, which registers the toll to their account
An ice cream truck is parked at a local beach and customers queue up to buy ice creams at a rate of one per minute. The arrival pattern of people buying ice cream is essentially random. It takes 40
Students arrive one at a time, completely at random, to an advice clinic at a rate of 10 per hour. Students take on average 5 minutes of advice but there is wide variation in the time they need; this
Patients arrive to a small hospital emergency room according to a Poisson process with an average rate of 1.5 per hour. Because service times for these patients vary considerably, the service times
Suppose that on average we observe 50 people at the beach and a rate of arrivals of one person every 3 minutes. How long, on average, do people spend at the beach?
Estimate the squared coefficient of variation of the arrival process. Is the arrival process likely to be Poisson? Why or why not? Estimate the arrival rate?
The following data has been collected on the number of customers seen to arrive to a doctor’s office in a succession of 15 minute intervals: 4, 5, 4, 3, 3, 3, 1, 2, 1, 3, 2, 4, 1, 2, and
The following data has been collected on the interarrival times of patients to an emergency department: 3.772, 1.761, 0.743, 15.988, 0.412, 7.541, 6.900, 3.447, 7.024, 1.061, 5.449, 0.309, 0.766,
Suppose that arrivals to a hairdresser follow a Poisson process with mean 12 customers per hour. Calculate the probabilities of (a) no customers in 20 minutes; (b) exactly one customer in 5 minutes;
Consider the following commercial bread making process. First, the dough is mixed in batches in the single mixer and it takes 15 minutes for a batch of dough that will produce 100 loaves. The batch
Give an example of an industry you have not seen revenue management applied to but that you believe it could be applied to. Why do you think it has not been used?
Give an example of an application of revenue management that you have seen or heard of outside of airlines and hotels. Describe how it is offered.
List the possible metrics that may be used by call centers to measure performance.Which of these are easiest to measure? Which are most important from the customer’s perspective?
Disney’s Fastpass system is free to all ticket holders but other theme parks, such as Universal Studios, charge a fee for priority queue access. Discuss the advantages and disadvantages of such
Write (and send) a letter or email to a firm detailing a recent service failure you have personally experienced. Analyze the reply (if any) with respect to the guidelines in Section 7.6.
Give an example of a service failure you have experienced. Was there any remedy given? What could the firm have done better?
Give an example of a service guarantee you are familiar with. How does it rate relative to the guidelines in Section 7.6?
Give an example of a firm that has recently introduced or increased the use of technology in its service offering. How did they perform relative to the three guidelines given in Section 7.6?
Consider your most recent unpleasant waiting experience. What went wrong and how could it have been improved?
Give an example (other than Disney) of a firm that you think is good at using queueing psychology. Explain your answer.
What are the advantages and disadvantages of queueing analysis versus simulation?
Modify Example 7.8 to find an example where pooling increases average waiting time across the two customer types.
At the SuperSpeedy drive-through the time between consecutive customer arrivals has a mean of 50 seconds and a standard deviation of 30 seconds. There are two servers whose service time averages 80
Customers send emails to a help desk that has three employees who answer the emails (and this is their only responsibility). Customer requests arrive according to a Poisson process with a rate of 30
Customers arrive to a local bakery with an average time between arrivals of 5 minutes. However, there is quite a lot of variability in the customers’ arrivals, as one would expect in an unscheduled
A teller works at a rural bank. Customers arrive to complete their banking transactions on average one every 10 minutes; their arrivals follow a Poisson arrival process. Because of the range of
Which of the three variables in Little’s law do you think is generally the most difficult to estimate (and why)?
Suppose that the billing cycle for a firm is 60 days and they invoice on average$5000 per day. What is the average total dollar amount of outstanding invoices that they carry?
A supermarket manager notices that there are 20 customers at the checkouts and also knows that arrivals to the checkout at that time of day are at a rate of about two per minute. About how long are
Suppose a bank has three tellers that are each busy 80 percent of the time. Estimate the probability of delay for a randomly arriving customer.
What does question 16 imply about whether an online and catalog retailer, such as L.L.Bean, should have regional or centralized call centers? What other considerations might come into this decision?
Recreate Figure 7–3 for a call center that wants to achieve a 40 percent no hold rate. Suppose that agents only become cost effective (where the revenue they generate exceeds their cost) if they
Estimate the squared coefficient of variation of the arrival process. If this data was known to come from a Poisson process, what would be your estimate of , the rate of customer arrivals?
The following data has been collected on the number of customers seen to arrive to a museum in a succession of 5-minute intervals: 5, 1, 3, 7, 5, 5, 6, 7, 5, 7, 4, 8, 1, 5, 2, 3, and

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