MGT 3121

At a hospital emergency room, patients come in at the rate of 20 per hour and on average, are processed at the rate as well. Patients wait in queue till they are called in for registration. After registration, patients are taken to an inner area where they are assigned a bed where they wait till an intern is ready to see them. Once an intern sees them, she either identifies them to be a routine case, prescribes medication and releases them, or she admits them to the hospital for further tests and treatment. On average, it is found that there are 30 patients waiting for registration and another 20 waiting to be seen by an intern. A study has determined that 75% of the patients simply require routine treatment. A new system separates the emergency room into two treatment areas, one for routine care and another for emergency cases. A triage nurse who assigns the patient to one of the two tracks sees a patient after registration. Patients for routine care are seen by an intern who either prescribes medication and releases them or determines that the triage nurse has made a mistake and the patient really needs emergency care. In this case the patient is moved to the emergency track. Patients for emergency care are seen by an intern who either admits them for further treatment or determines that they really are routine cases, prescribes medication and releases them. It is determined that there are, on average, 20 people waiting to be registered, 5 waiting to be seen by the triage nurse, 10 waiting to be seen by an intern in the emergency area, and 10 waiting to be seen by an intern in the routine care area. One average, 75% of the patients are classified by the triage nurse as needing routine care. (a) On average, how long did patients spend in the emergency room before the triage system (either before being released or admitted)? (b) On average, how long do patients that are finally admitted to the hospital spend in the emergency room after the introduction of the triage system? Assume that the triage nurse makes no mistake in identifying a patient as needing routine or emergency care. (c) On average, how long do patients spend in the emergency room after the triage system is introduced (either before being released or admitted)? Assume that the triage nurse makes no mistake in identifying a patient as needing routine or emergency care.

(a) Pre Triage process: Throughput = 20 per hour Average Inventory = 20 + 30 = 50 Average flow time = Average inventory / Throughput = 50 / 20 = 2.5 hours. (b) Triage Process: Registration: Average Inventory = 20 Throughput = 20 per hour Average flow time = 20 / 20 = 1 hour Triage: Average Inventory = 5 Throughput = 20 per hour Average flow time = 5 / 20 = 0.25 hour Admit: Average Inventory = 10 Throughput = 5 per hour Average flow time = 10 /5 = 2 hours Average time spent by people admitted = 1 + 0.25 + 2 = 3.25 hours (c) In this case we have Average Inventory = 20 + 5 + 10 + 10 = 45 Throughput = 20 per hour Average flow time = 45 / 20 = 2.25 hours.

Accounts Receivable (AR) receives an average of 1,000 payments per week. There is an average of 500 checks waiting to be deposited. (a) What is the average time spent by each check waiting to be deposited? (b) Assume that the checks coming in are either small or large. Small checks are for an average of $500 and large checks are for an average of $5,000. 20% of the checks coming in are large with the rest being small. Currently no distinction is made between the large and small checks. As a result 20% of the checks waiting to be processed are large. Is it worth reallocating resources so that large checks wait an average of 0.3 weeks while small checks wait an average of 0.8 week before being processed?

(a) Throughput R = 1,000 per week, Inventory I = 500. Thus flow time T = I/R = 500/1000 = 0.5 weeks. (b) Currently AR carries an inventory of 500 checks worth 500 0.2 5,000 + 500 0.8 500 = $70,000 waiting to be deposited. Now consider the case where resources are reallocated. Flow time of large checks = 0.3 weeks, throughput R = 200/week. Thus average inventory of large checks = 0.3 200 = 60 checks = 60 5,000 = $30,000. Flow time of small checks = 0.8 week, throughput = 800/week. Thus, inventory of small checks = 0.8 800 checks = 640 checks = 640 500 =$32,000. Total inventory in this case = $30,000 + $32,000 = $62,000. Since $62,000 is less than $70,000, the change will reduce the dollar value of checks waiting to be deposited and is beneficial. This is in spite of the fact that the average inventory of checks will increase from 500 to 860.

A summer camp that offers one week programs faces the challenges of long queues as parents try to check in their children each Saturday morning. If they were to add more staff to assist with the check-in process, then which of the following will occur: (i) the average time parents wait decreases, (ii) the maximum time the parents wait decreases, (iii) the average number of parents waiting to check in their child decreases.

(i), (ii) and (iii)

A machine is available 10 hours a day. Each part takes 90 minutes to fabricate and 10 minutes to setup. 10% of the parts made are defective and must go through the machine again to be reworked, during which both setup and fabrication have to be performed again. The machine is idle for any unused time. On average, 5 good parts are made each day. What is the overall equipment effectiveness of the machine?

0.75, Total time available = 10 × 60 = 600 minutes. Value added time = 90 × 5 = 450 minutes. OEE = 450 / 600 = 0.75.

What is the maximum utilization a resource can achieve?

1.00

Patients are arriving at a clinic at a rate of two per minute. Each patient's visit consists of four steps: check in, record vital signs, receive treatment, and check out. A receptionist takes 1 minute to check a patient in. A nurse takes 2 minutes to record the patient's vital signs. A doctor spends 10 minutes with a patient. A staff member takes 3 minutes to check a patient out. What is the process capacity in patients per hour?

30 , Capacity = 1/Processing time. Capacity at check in, record vital signs, receive treatment, and check out is 1, 0.5, 0.1, and 0.3 patient per minute respectively. The lowest capacity is the bottleneck and is Process capacity = 0.1 patient per minute = 0.1 × 60 (minutes/hour) = 6 patients per hour.

C&A makes two flavors of ice cream - chocolate and vanilla. Each gallon is produced and shipped in discrete containers. The demand for the ice cream (in gallons) is given as follow:

4.7 minutes per gallon, alternate between 1 unit of chocolate and 2 units of vanilla. Available time = 8 × 60 × 5 = 2400 minutes. Total demand = 20 + 40 + ... + 100 = 510 gallons. Takt time = available time / demand = 2400/510 = 4.7 minutes per gallon. Total chocolate demand = 170 gallons. Total vanilla demand = 340 gallons. There is twice as much demand for vanilla as chocolate. Therefore, a level production schedule should alternate between 1 unit of chocolate and 2 units of vanilla.

Daily demand for a product is 200 units. The production lead time is 2 days. A 1-day safety stock is kept. How many kanban containers will be needed if one container holds 100 units?

6, Demand during lead time + safety stock = 2 × 200 + 1 × 200 = 600. Number of Kanban container = 600/100 = 6.

C&A uses an assembly line of 20 stations to make a product. The cycle time is 5 minutes per unit. Step 6 is the most error-prone operation. Inspection occurs at the last station. What will be the information turnaround time for a defect made at station 6 if there is no inventory between stations?

70 minutes, There are 14 stations between stations 6 and 20. It takes 14 cycles of 5 minutes each for the flow unit to be completely tested. Therefore, the information turnaround time = 14 × 5 = 70 minutes.

Which of the following statements is FALSE?

A bottleneck resource must have a utilization of 100%.

Which of the following is an example of overengineering?

A building that can withstand a major earthquake

Which of the following is NOT a rule to define a flow unit?

A flow unit should be used to measure the number of resources in a process.

Which of the following statements is TRUE about economies of scale in queuing systems?

A large system is more efficient than a small system.

Which of the following is the correct definition of a robust process?

A robust process is one that can tolerate variations in input and environmental variables without an increase in outcome variation.

Which of the following is an example of foolproofing?

A saw that will not start if the blade is not inserted properly in its housing

Which of the following is a definition of the term "process"?

A set of activities that transforms a collection of inputs into outputs.

Which of the following items would be considered resources in a restaurant?

Chefs

Which of the following best reflects pooling capacity to reduce restroom queue lengths?

Convert the separate men's and women's rooms into a single unisex restroom (that both men and women can use).

Which of the following is not a dimension or sub-dimension in a customer's utility function?

Customer Satisfaction

The process is ___________ constrained when ___________ exceeds ___________ and the flow rate is equal to the demand rate.

Demand, supply, demand

Is the capacity of the bottleneck larger than, equal to, or smaller than the capacity of the process?

Equal to

A computer server experiences large fluctuations in the amount of data requests it receives throughout the day. Because of this variation, Little's Law does not apply.

False

The efficient frontier is given by the cheapest company in the industry.

False

There can be no more than two firms on the efficient frontier.

False

Which of the following is not one of the three system inhibitors?

Fatigue

____________ illustrate how the ___________ variable is being influenced by the input and ____________ variables.

Fishbone diagrams, outcome, environmental

A patient spent 25 minutes waiting in the reception area before seeing a doctor. The visit with the doctor lasted 5 minutes. What is the value-added percentage of the patient?

Flow time is 25 + 5 = 30 minutes. Value-add time is 5 minutes. Therefore, the value-add percentage = 5/30 = 0.17 = 17%.

A process analysis of a hospital's emergency room can answer all of the following questions EXCEPT:

How busy are the physicians in the outpatient clinic?

Which of the following questions would be asked in a process analysis of a college admissions office?

How long does it take the office to process an application?

Which of the following is not related to Operations Management?

How much do we pay the CEO?

A product sold at a supermarket has a shelf life of 21 days. If daily demand averages 100 units, what is the maximum inventory that the supermarket should carry.

In this case, throughput R = 100 /day. The maximum flow time cannot exceed 21 days (ideally should be much lower). Thus the supermarket should carry a maximum of 21100 = 2,100 units in inventory. Ideally, the inventory carried should be significantly lower.

YourNurse (YN) Inc uses certified nurses to answer medical queries from customers over the phone. When patients call into YN they are first asked to provide their zip code which then allows YN to route their call to the call center nearest to the patient (they operate 10 across the country). Which single suggestion in the following list (and explanation) is most likely to reduce the average time callers wait before speaking with a nurse?

Instead of using callers' zip codes, route calls to the call center with the fewest callers to help prevent situations in which there are idle nurses at the same time that there are callers on hold.

SmartPhones are made on a 40-step assembly process. All 40 steps are connected through a conveyor belt and all of the 40 steps must work at the same rate even if some of them have more capacity than others. Is this process a machine-paced process or a worker-paced process?

Machine-paced

Which of the following is a way to reduce a queue by adjusting capacity?

Minimize the amount of work that needs to be done during peak time

From the perspective of process analysis, which of the following could be appropriate flow units for a hardware store?

Number of customers

Over the course of a month, which of the following is most likely to describe an appropriate flow unit for a process analysis of a hospital?

Number of patients

Which of the following statements about resources of a process flow diagram is TRUE?

Outputs of some resources can be used as inputs to other resources.

________ and ________ are ways to reduce a queue by adjusting demand.

Peak-load pricing, off-peak discount

You observe a vehicle registration department at your local township. Assume that all employees are ready to work at 9 a.m. You arrive at 9 a.m. sharp and are the first customer. Is your time through the empty process longer or shorter than flow time averaged across all customers that arrive over the course of the day?

Shorter than the average flow time

A firm has seen its demand quadruple over a 2 year period. During the same period, the number of turns has doubled. What has happened to inventories over the same period?

Since turns have doubled, flow time is half of what it was. Throughput (demand) meanwhile has increased by a factor of 4. Thus inventories should have increased by a factor of 0.5* 4 = 2 over the same period. Inventories have thus doubled.

Queuing system A has a utilization of 80% and queuing system B has a utilization of 90%. Both have a single server. Say the utilization of both systems increases by 5%, i.e., A increases from 80% to 85% while B increases from 90% to 95%. Which system is likely to experience the biggest change in the average time in queue?

System B

What is the key assumption for the single-server queue model?

The capacity of the server is less than the demand rate.

You observe a bank and notice that a customer leaves the bank about every 5 minutes. These 5 minutes between customers are:

The cycle time

Which of the following statements about queues is FALSE when demand exceeds supply?

The queue grows as long as the supply rate exceeds capacity.

C&A operates a dry cleaning service. Which of the following is an input variable for C&A?

The temperature of the dry cleaning machine

What is the relationship between the processing time at a resource and its capacity?

They are reciprocals of each other

Customers walk into a bank and are served at an average rate of 20 per hour. One average there are 5 people waiting in queue to be served. How long does the average customer wait in queue?

Throughput R = 20 per hour, Inventory I = 5 Waiting time in queue T = I/R = 5/20 = 0.25 hours = 15 minutes.

For the purpose of process analysis, which of the following is measured in an appropriate flow unit for analyzing the main operation of a department store?

Weekly sales figure

When will the utilization of a bottleneck resource be less than 100%?

When the process is demand constrained

Which of the following statements is FALSE regarding the waiting time in a single-server queue model?

When utilization increases, the average waiting time decreases.

Two retailers compete on costs and ambiance of the retail store. They are identical on all other dimensions of customer utility. Retailer A is cheaper than retailer B. Retailer A also has the better ambiance. Does this mean that retailer A is on the efficient frontier?

Yes

p-charts are also called ___________.

attribute-based control charts

When a process has economies of scale in the operations of a system with queues, it means a _________ queue system can be more _________.

bigger, efficient

A pooled queue system increases the _________ of the __________ process.

flexibility, supply

Process utilization is the ratio between __________ and ______________.

flow rate, process capacity

An indicator of inefficiency in a separate queue system is:

having idle servers and waiting customers at the same time.

Flow rate tells us:

how much stuff moves through the process per unit of time.

The drivers of waiting time in a single-server queue system include all of the following EXCEPT:

learning.

The capacity of a resource determines the ___________ number of flow units that can flow through that resource per unit of time.

maximum

A process metric is something that can be __________ to reveal the ____________ and ____________ of a process.

measured, performance, capability

Over the course of a day, fans pour into NASCAR venue at the rate of 8,000 people per hour. The rate at which fans leave the venue...

must be exactly 8,000 people per hour

An X¯¯¯ chart has __________ on the x-axis and _____________ on the y-axis.

time periods at which samples are taken, sample means

You observe a long line at the airport security. The process is currently:

Capacity constrained

Which of the following statements about a control chart is correct?

It is possible that the outcome of a process is within the control limits but outside the specification limits.

Which of the following statements is TRUE?

Utilization of a resource is at its maximum when the flow rate is equal to its capacity.

If you are to monitor the number of customers who are not satisfied with your services, which of the following control charts will you use?

p-chart

A graphical representation of a process is called a:

process flow diagram.

The _______________ of a resource is how long that particular resource takes to complete one flow unit.

processing time

A flow unit is:

the basic unit that moves through a process.

The data that should be collected in order to construct a Pareto diagram include all of the following EXCEPT: causes of defect.

the bottleneck location

From the perspective of a cashier in a supermarket, the appropriate level for the process scope is:

the customer checkout process.

A process scope is:

the set of activities involved in the process.