Chapter.10 Process Variability & Losses Test Bank Answers 4e

Matching Supply with Demand: An Introduction to Operations Management, 4e (Cachon)

Chapter 10 The Impact of Variability on Process Performance: Throughput Losses

[The following information applies to questions 1-2.]

Airport Massage Station

A small company just opened a new massage station at the Philadelphia airport. The company has a stand that offers massages to travelers. Customers can select a length of time for a massage between 5 and 20 minutes, and there is a unique rate of $30 independent of the length of time chosen by customers. The average massage length, requested by customers, is 15 minutes with a standard deviation of 10 minutes. There are four employees delivering massages. The average number of potential customers requesting a massage is 20 per hour. The interarrival times are assumed to be exponentially distributed. If spots are unavailable when the customers arrive, they leave in order not to risk missing their flights.

1) What is the average number of customers being serviced per hour at the massage station? Choose the closest answer.

A) 7

B) 8

C) 9

D) 10

E) 11

F) 12

G) 13

H) There is not sufficient information to answer the question.

Difficulty: 2 Medium

Topic: Motivating Examples: Why Averages Do Not Work; Throughput Loss for a Simple Process

AACSB: Knowledge Application

Blooms: Apply

2) The station manager is considering the option of hiring additional employees to deliver massages. The hourly wage of an employee is $50/hr. How many ADDITIONAL employees should the manager hire to maximize profits?

[Profit = revenues from customers - labor cost]

Suppose that there exists sufficient equipment to accommodate as many new employees as needed.

A) none

B) 1 additional employee

C) 2 additional employees

D) 3 additional employees

E) 4 additional employees

F) There is not sufficient information to answer the question.

Difficulty: 2 Medium

Topic: Throughput Loss for a Simple Process

AACSB: Analytical Thinking

Blooms: Analyze

[The following information applies to questions 3-6.]

Hospital Trauma Bays

The local hospital's emergency department has 6 trauma bays. On average, patients requiring a trauma bay arrive every 30 minutes with a coefficient of variation of 1 (no seasonality exists). If the hospital has an available trauma bay, it is immediately allocated to a needy patient. If there are no trauma bays available, the patient is sent to another hospital. On average, a patient's length of stay in a trauma bay is 1.5 hours (with a standard deviation of 1.5 hours). The hospital's emergency department operates 24 hours a day.

3) What percentage of the patients requiring trauma bays end up being sent to another hospital?

Difficulty: 3 Hard

Topic: Throughput Loss for a Simple Process

AACSB: Knowledge Application

Blooms: Apply

4) How many patients are treated in the trauma bays on an average 24-hour day? (Round to the nearest whole number).

Difficulty: 3 Hard

Topic: Throughput Loss for a Simple Process

AACSB: Knowledge Application

Blooms: Apply

5) The hospital updated the operating procedures for its staff. This led to a reduction in the coefficient of variation of the length of stay in a trauma bay from 1.5 to 1.25 and a reduction in the mean to 1 hour. How will this training program affect the number of patients who have immediate access to a trauma bay?

Difficulty: 3 Hard

Topic: Throughput Loss for a Simple Process

AACSB: Reflective Thinking

Blooms: Analyze

6) New state regulations require that every emergency department be able to accommodate at least 90% of all patients needing a trauma bay without any waiting. What is the minimum number of trauma bays necessary to meet this requirement? (Note: Assume that the time spent in the trauma bay cannot be changed.)

Difficulty: 3 Hard

Topic: Throughput Loss for a Simple Process

AACSB: Reflective Thinking

Blooms: Analyze

[The following information applies for questions 7-9.]

Doc on call

A company has started a phone service that uses overseas doctors to provide emergency medical consultations. The responding doctors are based in a country with low wages but with a highly skilled pool of physicians. Responding to each call takes, on average, 15 minutes. At any given time, there are 4 doctors overseas on duty. Calls arrive every 5 minutes on average (standard deviation is 5 minutes). The company receives $50 from the patient's insurance company for each consultation. If one of the 4 overseas doctors is available, the firm pays $20 to the doctor and makes $30 in profit. If no doctor is available overseas, the call is rerouted to the U.S. where a local physician answers the question. A local physician is always available to take a call. In this case, the firm pays the $50 to the local physician, so there's no profit for the company.

7) What is the probability of a call being answered by a physician in the U.S.? (Round to four decimal places)

Difficulty: 3 Hard

Topic: Throughput Loss for a Simple Process

AACSB: Knowledge Application

Blooms: Apply

8) What would be the additional revenue per hour obtained if the company managed to have 10 doctors overseas on duty at any given time?

Difficulty: 3 Hard

Topic: Throughput Loss for a Simple Process

AACSB: Reflective Thinking

Blooms: Analyze

9) What would be the additional profit if the company managed to have 10 doctors overseas on duty at any given time?

Difficulty: 3 Hard

Topic: Throughput Loss for a Simple Process

AACSB: Knowledge Application

Blooms: Apply