Question 1

Most of the delay in the opening of the Denver International Airport was because of problems with
A) the air traffic control system
B) the environmental monitoring systems
C) the baggage handling system
D) the telephone and communications systems

Accepted Answer

The primary cause of the delay in the opening of the Denver International Airport was due to issues with the automated baggage handling system, which was highly complex and faced numerous technical problems.

Question 2

One of the sources of failure common to BOTH the Therac-25 and the Ariane 5 rocket was
A) confusing and poorly-documented error messages
B) poor human-computer interface design
C) operator error
D) reuse of software from previous versions of the systems

Accepted Answer

Both the Therac-25 radiation therapy machine and the Ariane 5 rocket experienced failures due to the reuse of software from previous versions of their systems without adequate testing and adaptation for the new contexts in which they were deployed.

Question 3

Which of the following occupations can sometimes cause Repetitive Strain Injuries (RSI)?
A) Sign-language interpreter for the deaf
B) Musician
C) Computer programmer
D) All of the above

Accepted Answer

All of the listed occupations involve repetitive motions or positions that can lead to Repetitive Strain Injuries (RSI). Sign-language interpreters, musicians, and computer programmers all perform tasks that can strain certain muscle groups or joints through repetitive use.

Question 4

List two principles for producing software that might have prevented the crash of American Airlines Flight 965 near Cali, Columbia in 1995. Briefly describe what each one is and how it might have made a difference.

Accepted Answer

The answer of List two principles for producing software that...

Question 5

Briefly explain the Therac-25 case. What happened? What are some reasons the machine failed? Why were there so many incidents?

Accepted Answer

The answer of Briefly explain the Therac-25 case. What happened?...

Question 6

Some computer errors are actually system failures, in that it was the human/computer interface which caused the resulting problem.

Accepted Answer

Many computer errors can indeed be attributed to issues at the human/computer interface, where poor design, user error, or misunderstandings about the system's functionality lead to failures.

Question 7

The cause of failure in a computer program is often due to more than one factor.

Accepted Answer

Computer programs can fail due to a variety of factors including bugs, hardware malfunctions, incorrect input, and integration issues with other systems, often interacting in complex ways.

Question 8

Legacy systems are typically reliable, but inflexible.

Accepted Answer

Legacy systems are often considered reliable because they have been used and tested over time. However, they are inflexible because they may not easily integrate with newer technologies or adapt to changing business needs.

Question 9

U.S. and European pilots are now trained to follow Traffic Collision Avoidance System (TCAS) instructions even if they conflict with instructions from an air traffic controller.

Accepted Answer

Pilots are trained to prioritize TCAS advisories over air traffic control instructions to avoid mid-air collisions, as TCAS provides real-time collision threats based on the immediate positions and velocities of aircraft.

Question 10

Redundancy and self-checking are often present in safety-critical systems.

Accepted Answer

Redundancy and self-checking mechanisms are commonly used in safety-critical systems to enhance reliability and ensure that the system can continue to operate correctly even in the case of a failure.

Question 11

A feature of high reliability organizations is loose structure.

Accepted Answer

High reliability organizations are characterized by a tight structure, with clear roles and responsibilities, and a strong emphasis on following procedures.

Question 12

Some people have proposed establishing legal standards and regulations to govern safety-critical computer-based systems. 
a. Give and explain a few of the best arguments for and against such a proposal (at least two on each side). Give counter-arguments against the arguments for each side.
Note: the "counter-arguments"
you are asked to give should oppose or answer the arguments on the other side as directly and convincingly as possible. They should not be simply unrelated arguments on the opposite side of the issue.
b. Describe two provisions that may be included in such regulations. How effective do you feel each provision would be?

Accepted Answer

The answer of Some people have proposed establishing legal standards...

Question 13

a. Describe the role the manufacturer, the hospitals/clinics, and the programmer each played in the Therac-25 radiation overdose incidents.
b. Briefly describe how professional techniques for increasing reliability and safety could have prevented the problems.

Accepted Answer

The answer of a. Describe the role the manufacturer, the...

Question 14

a. Briefly describe the major factors that contributed to the failure of each of the following: the Denver Airport baggage system failure, the Ariane 5 rocket malfunction, and an A320 Airbus crash. 
b. Briefly describe how professional techniques for increasing reliability and safety could have prevented these failures.

Accepted Answer

The answer of a. Briefly describe the major factors that...

Question 15

MATCHING
-Therac-25
A) a computerized machine that gave lethal radiation overdoses to some cancer patients
B) operate in difficult environments where failures can have extreme consequences
C) detects a potential in-air collision of two planes and directs the pilots to avoid each other

Accepted Answer

Therac-25 was a computerized radiation therapy machine involved in several accidents where patients received lethal doses of radiation due to software errors and inadequate safety mechanisms.

Question 16

MATCHING
-HROs
A) a computerized machine that gave lethal radiation overdoses to some cancer patients
B) operate in difficult environments where failures can have extreme consequences
C) detects a potential in-air collision of two planes and directs the pilots to avoid each other

Accepted Answer

High Reliability Organizations (HROs) operate in challenging environments where the consequences of failure can be severe, requiring them to maintain high levels of safety and reliability.

Question 17

MATCHING
-TCAS
A) a computerized machine that gave lethal radiation overdoses to some cancer patients
B) operate in difficult environments where failures can have extreme consequences
C) detects a potential in-air collision of two planes and directs the pilots to avoid each other

Accepted Answer

TCAS (Traffic Collision Avoidance System) is designed to detect potential in-air collisions between aircraft and provide instructions to pilots to avoid such incidents.

Quiz 8: Errors, Failures, and Risks

Most of the delay in the opening of the Denver International Airport was because of problems with

One of the sources of failure common to BOTH the Therac-25 and the Ariane 5 rocket was

Which of the following occupations can sometimes cause Repetitive Strain Injuries (RSI) ?

List two principles for producing software that might have prevented the crash of American Airlines Flight 965 near Cali, Columbia in 1995. Briefly describe what each one is and how it might have made a difference.

Briefly explain the Therac-25 case. What happened? What are some reasons the machine failed? Why were there so many incidents?

Some computer errors are actually system failures, in that it was the human/computer interface which caused the resulting problem.

The cause of failure in a computer program is often due to more than one factor.

Legacy systems are typically reliable, but inflexible.

U.S. and European pilots are now trained to follow Traffic Collision Avoidance System (TCAS) instructions even if they conflict with instructions from an air traffic controller.

Redundancy and self-checking are often present in safety-critical systems.

A feature of high reliability organizations is loose structure.

a. Describe the role the manufacturer, the hospitals/clinics, and the programmer each played in the Therac-25 radiation overdose incidents. b. Briefly describe how professional techniques for increasing reliability and safety could have prevented the problems.

MATCHING -Therac-25

MATCHING -HROs

MATCHING -TCAS