Project #14415 - Operations & Supply Chain Management

Here are the questions I need answered. Please do not forget to show your work in some of the questions. Thank you - Homework due Sunday October 13th 2013 at midnight.


Part I - Quality Control Homework


  1. Southwest keeps gate time of its planes at a minimum in order to maximize the flying time, hence capacity utilization of its planes. They want to achieve a turnaround time of 21 minutes on average with a maximum of 25 minutes and a minimum of 17 minutes. (Although faster would be fine with them, the FAA and passengers might think they are cutting corners and not doing everything correctly.) At the Baltimore airport (BWI), 3 gates a day were sampled over four days to determine how the Southwest ground crew at BWI was doing on this standard. The average of the process was 20.5 minutes and the standard deviation was 1.3 minutes.


    1. Fill in the following table.








    1. Is the process centered and capable? Why or why not?



    1. What is the probability that a plane will have a turnaround time of greater than 24 minutes? Draw the appropriate diagram and find the probability.










Part II - Queuing Homework


You have recently become the manager of the Patriot Airlines check in counter. Because Patriot Airlines has flights that leave frequently all day, customers arrive randomly (i.e., exponentially distributed) at the counter at the average rate of 3 per minute. There is only one employee at a time to staff the counter. Assume the employee takes on average 17 seconds to serve each customer. You may assume this is exponentially distributed.


a)      Please fill in the following table. Please include the units.



Average interarrival time




Average service time





b)      What is the average number of customers in line?


c)      What is the average number of customers in the system?


d)      What is the average waiting time in line?


e)      What is the average waiting time in the system?


f)       When the employee is not serving customers, he answers complaint letters regarding service at the airport. If the employee works an 8 hour shift, how much time on average does he have to devote to this activity during the shift?


g)      Suppose that, as a result of customer complaints, you decide you need two employees working at the same time. You hire someone so there are two employees but now on average, the service time has a mean of 24 seconds and the variability is 45 sec2.


Please fill in the following table. Please include the units.




Average service time











Part III - Capacity Homework


Each circle below represents a single server (one worker per station) and the time indicates the time for a single customer/job. There is no variability in service times and no buffers. Please use the metrics discussed in class to analyze and summarize these systems (independently from one another, you do not need to compare them). Don’t forget to put units.


Station 2

20 min


Station 1

25 min




Cycle Time


Flow Time




Utilization Station 1


Utilization Station 2




Station 2

22 min


Station 1

18 min



Cycle Time


Flow Time




Utilization Station 1


Utilization Station 2



d. Describe what are blocking and starving and how they occur in parts a and b?



Part IV - Inventory Homework


1. Southside uses a fixed quantity (continuous replenishment) system. Daily demand for bags of coffee is normally distributed with a mean of 36 and standard deviation of 8, and lead time is constant at 5 days. The management wants to have a 92 percent service level and the dining hall is open 365 days per year. Holding costs are $0.50 per year and the ordering costs are $2.5 per order. Answer the following.


a.       What is the EOQ?


b.      What is the safety stock level required?


c.       What is the reorder point?


d.      What is the optimal inventory policy?


Part V - Short Answer Questions Homework


Read the QSR Drive-Thru article and answer the following questions:

Article Links:



1. Why does a wider variety on the menu increase service times? How does this impact the waiting times and specifically what variable in the queuing analysis changes?


2. When Krystal reduced its average service time by 40 seconds, how does this decrease the average number of customers waiting in line?


3. How does customer-introduced variability affect the drive-thru process? Identify and briefly describe three ways. Then identify 2 possible ways to deal with each type of variability and classify each using the customer-introduced variability matrix. You may use the table to answer.


Type of Customer-Induced Variability


First way to deal and Classification

Second way to deal and Classification



















Read the HP and the Silk road article (“Hauling New Treasure Along the Silk Road”) link and answer the following.


1. Identify and explain (1-2 sentences each) two operational trade-offs mentioned in this article.


2. Which model (equation(s)) that we discussed is relevant to this article? Why? Describe the model and how it applies to the article.


3. The article mentions that the sea route is cheaper, but the cost of the added time by sea is considerable. How might you incorporate this cost into a model to compare sea versus silk road shipping? In other words, where does this cost “go” in terms of the parameters and how would you use it to compare the two options.


4. Compare the supply chain risks of the sea route versus the silk road route. Be specific. Given the risks, how does HP endorse the silk road route? What do they do or should they do to mitigate the risks?


Other Short Answer

1.   Warranty costs are an example of __________________ costs of quality.


2.   In the analogy of “rocks in the river/pond” to inventory management and lean manufacturing, the river represents ____________________ (operations problems / inventory / orders).


3.   In a push system, work in process inventory piles up at the ____________________________.


4.       The main focus of a responsive supply chain is to minimize ____________________(cost / lead time), whereas the main focus of an efficient supply chain is to minimize ____________________ (cost / lead time).  Canned tuna is best served by a(n) _______________ (efficient / responsive) supply chain; the Tesla Roadster (fancy and expensive sport car, 100% electric) is best served by a(n) _____________ (efficient / responsive) supply chain. 

5.    The best case was ________________________________________because:


Part VI - Multiple Choice questions and True or False answer homework


Multiple choice: Please circle or underline or choose the right answer.


1.      Animal shelters tend to order sodium barbipentathol in large batches (e.g., enough to last 6 months or more).  Smaller quantities would be ordered (e.g., a couple of weeks worth) except government regulations require extensive and detailed paperwork to be submitted with each order.  This example is most closely related to the following managerial insight:

a.       the order quantity increases as the holding cost rate decreases

b.      the order quantity increases as the cost per order increases

c.       the order quantity increases as the shortage cost rate decreases

d.      the order quantity increases as the trade balance decreases

e.       All of the above


2.      Which one of the following does not exemplify JIT/Lean used for competitive advantage?

a.       Acme Foods decides to decrease the number of its suppliers to just a few.

b.      Cajun Contractors has reduced the amount of space for inventory.

c.       Cheramie Trucking trains workers to specialize and become very efficient in one job.

d.      Ardoyne Builders has a scheduled preventive maintenance program.

e.       Ajax, Inc. is proud to announce that incoming goods are delivered directly to the point of use.


  1. A tennis ball manufacturer has identified several causes of variability in the bounce and has collected data on the number of times those causes have led to high variability over the past month. They now need to decide which causes to try to eliminate first. Which tool should they use?

a.     5S

b.    Pareto diagram

c.     ABC Analysis

d.    R-chart

e.     PDCA


4.      Another term for a postponement strategy is

a.       Speculation

b.      delayed differentiation

c.       mass customization

d.      decreased differentiation

e.       None of the above

5.      Which of the following offers a potential for reducing inventory costs in a supply chain?

a.       sharing POS data across the supply chain

b.      sharing components across different products                      

c.       having more warehouses

d.      using slow transportation modes

e.       a and b

f.       a and c

g.      b and c

h.      c and d


6.      Which of the following phrases describes the chart below about the reasons for unsatisfying hotel stays?

a.       H is the most important problem

b.      80% of the reasons cause 20% of the dissatisfaction.

c.       A is the most important problem

d.      20% of the reasons cause 60% of the dissatisfaction

e.       None of the above.



7.   If the EOQ is calculated to be 100 units and the annual demand is 5,000 units, what is the time between orders if the company works 300 days per year?

a.                               0.17 days

b.                               6 days

c.                               10 days

d.                              50 days

e.                               None of the above


8.         The purpose of safety stock is to

a.                                  protect the firm from a sudden decrease in demand

b.                                  replace failed units with good ones

c.                                  eliminate the possibility of a stockout

d.                                 control the likelihood of a stockout due to the variability of demand during lead time

e.                                  eliminate the likelihood of a stockout due to erroneous inventory tally



9.         Suppose you had to produce 700 units in 160 hours to meet the demand requirements of a product.  What is the cycle time to meet this demand requirement?

a.       0.22 min/unit

b.      4.4 units/hour

c.       10.3 min/unit

d.      13.7 units/hour

e.       None of the above


10.  The average demand rate is 100 per day.  The time in the system is 3 days.  This means that the average number in the system is

a.       33

b.      60

c.       120

d.      300

e.       None of the above


11.     It takes an average of 30 minutes to change the oil at Vanessa’s Quick Lube.  Average demand is 3.2 customers per hour.  What is system the utilization if there are 2 servers (e.g., 2 service bays that are used for changing oil)?

a.       5.3%   

b.      10.7%   

c.       62.5%    

d.      80.0%    

e.       more than 100%



1.        ________ Variation in production systems that is caused by factors that can be clearly identified and possibly even managed is called assignable variation.

2.        ________ EOQ balances purchase cost and ordering cost. 

3.     _________ Your supplier’s supplier is a third tier supplier.

4.        ________ Under the assumptions of the Basic EOQ model, if one increases the order quantity, then the length of the order cycle decreases (with demand and cost parameters remaining the same). 

5.     ________ A high-end, customized furniture manufacturer, would most likely employ an assembly-line type of process. 

6.     ________ Productivity is the total value of outputs produced divided by the total value of all inputs to the transformation process.

7.     _________ The idea behind Pareto charts is that working with the majority of possible causes is needed to significantly improve quality.

8.        ________ Under the assumptions of EOQ model, if the total optimal cost (fixed ordering cost + holding cost) is $10,000, then the holding cost part is $5,000.





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Due By (Pacific Time) 10/13/2013 12:00 am
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