Deck 8: Errors, Failures, and Risks

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

Answer 1

the baggage handling system

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

Answer 2

reuse of software from previous versions of the systems

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

Answer 3

All of the above

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.

Question 5

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

Question 6

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

Question 7

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

Question 8

Legacy systems are typically reliable, but inflexible.

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.

Question 10

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

Question 11

A feature of high reliability organizations is loose structure.

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?

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.

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.

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

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

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