Midterm SD142 , Spring 2003. 

1.     a. (8 marks)  Use the Human Action Cycle to describe the events in “Set Phasers on Stun”. 

 

Goal:  Give proper radiation treat to patient after his surgery for removal of tumor

Intention: Use Therac-25 cancer radiation therapy machine

Sequence of Actions:        Place patient underneath machine

                                          Go to control room

                                          Enter commands into keyboard (e for electron beam)

                                          Initiate treatment by pressing b for turning beam on

Actions: Same as above sequence, however she pressed “x” instead of “e” , pressed up, edits and reenters “e” then follows  to beam ready, and presses b

World: Patient hit by massive radiation, error appears on screen of display,

Perception: Mary Beth sees the error on her screen but doesn’t see that patient is hit with massive radiation

Interpretation: Mary Beth thinks that machine hadn’t fired and tries to repeat the procedure again. (does this 3 times), She thinks patient hasn’t received treatment yet

 

Evaluation: proper radiation treatment has not been given to patient but Mary do not know what has happened in the room. Her goal is not met

 

Marking notes: Above is the best answer. Some may have different goals or intentions, as long as the cycle is followed through you got full mark. 1 mark for each step’s label and description.

     

 Question 1a,1b,1c was marked by: Roshanak

 

 

1.     b. (4 marks) Identify the gulf of evaluation in Set Phasers on Stun.

 

There is no information on

the state of the world

there is no information to perceive

there is no information to interpret

there is no information to evaluate.

 

Marking notes: The best answer was to use the 4 steps of the Action Cycle and refer to the Gulf of Evaluation in this case study. Above is the best answer. You could either use the Action Cycle or use the “missing feedback from Machine, Patient and World for this. You needed to have complete answer in any case. Therefore you may have comments on your paper but got the full mark. 

 

 

1.c. (3 marks) What feedback should Mary Beth have had?

Mary Beth should have had feedback on

  1. the state (or mode) of the machine
  2. the output of the machine
  3. the state of the patient

These three pieces of information would have bridged the gulf of evaluation.

Marking note: Each point is worth 1 mark, and the points are derived from the human interface model.

     

 

     

2. In “the Wizards of Wall Street”, the broker sells the wrong amount of stock. Is his error best attributed to feather analysis or top down processing? Explain why. (3 marks)

 

* Key here is best

 

 

 

Marked by Brian

3. a. Bob has decided to skip his 1B co-op term and instead go gambling in Vegas.  He has to decide between the following casino games.  Use Expected Value theory to decide which game Bob should play.  (6 marks)

Game

Potential Winnings

Probability of Winning

Black Jack

150, 000

.0001

Roulette

97, 000

.0002

Craps

300, 000

.00005

Poker

250, 000

.00007

Slot machines

50, 000

.002

 

 

Blackjack EV=150,000*.0001 = $15.00

Roulette EV=$97000*.0002=$19.40

Craps EV=$300, 000*.00005 = $15

Poker EV=$250, 000*.00007=$17.50

Slot machines EV=50,000*.002=$100

 

By expected value theory, Bob should play Slot machine.

 

Marking Note: 1 mark for each calculation and 1 mark for picking the best decision.

 

Marked by Brian

 

 

 

3. b. (2 marks) Bob has decided that he would like to buy a house in Waterloo to live in.  The house he has picked out costs $150, 000.  In weighting his options, Bob considers winning $150, 000 or more to be twice as important as winning anything less, since this way he could buy the house.  Use this information in a Subjective Expected Utility Model to decide which casino game Bob should play now.

 

With the new information bob should still play the slot machine.

 

Marked by Brian

 

 

4.  (3 marks) In the following figure, three possible user interfaces for a banking program are shown.  With which interface will people move to the second screen the fastest, and why?

 

 

 

 

The first interface has 5 choices with small buttons, the second three choices with large buttons, and the third three choices with small buttons.  Using the Hick-Hyman law, the 3 choice interfaces (2 and 3) will have faster reaction times than the first one.  Using Fitt’s law, the second interface will have faster reaction times than 1 or 3.  By this argument, the 2nd interface should have the fastest time.

 

Marking note: 1 mark for using the Hick Hyman law correctly.

1 mark for using Fitts Law correctly

1 mark for making the right decision

 

Marked by Prof Burns

5. (8 marks) In An Act of God, Bill must make several decisions affecting the distribution of electrical power to New York City. Describe the four different categories of biases and discuss how they may have affected Bill's ability to make effective decisions on the night of the lightning strike in the case study. Be sure to give examples from the case study.

The 4 biases are input biases, hypothesis generation biases, hypothesis selection and evaluation biases, and action selection biases.

For input, Bill weighted the earliest incoming information heaviest. He did not search very far for information, including not going to the room that had the right display. For hypothesis generation Bill had one hypothesis and stuck to it and did not come up with new ideas. For selection, he rejected Kennedy's alternative, even though Kennedy was right. For action selection, most people argued that he talked on the phone rather than taking the necessary actions to correct the situation, therefore demonstrating not taking action.

4 marks for biases well explained. 4 marks for connecting them to the story correctly. 8 marks total.

Marked by Prof Burns

6.a.  (3 marks) In "In Search of the Lost Cord", Karen selected the wrong cord. Explain how her working knowledge created this situation. Explain how a designer could have taken advantage of working knowledge to prevent this accident.

With working knowledge people are not as precise. They are only as precise as they need to be. Since the cords were usually designed to be different and not fit, Karen did not need to precise about picking the cord. (this explanation was worth 2 marks)

A designer should have made it so that the cord did not fit. Karen would have recognized that immediately. Worth 1 mark.

Marked by Brian

6.b. (5 marks) Explain why the electrocution described in “In Search of the Lost Cord” could be considered a system accident.

In considering a system, one needs to look at the entire hospital room and the biology of the patient itself.  The important points are

a.     proximity between the devices, and in particular their cords.

b.     tight coupling of the human patient with respect to electrical charge, i.e. it doesn’t take a lot of electrical charge to change patient state, for the worst.

c.      non-linearities.  Once connected there is a nonlinearity between the power source and the patient.  Possibly a more robust argument are the nonlinearities inherent in biological systems.

d.     common-mode interactions.  There are many common mode connections in biological systems.

e.      limited ability to isolate components in the patient

f.       multiple unintended feedback loops in the patient.

g.     tightly spaced organs, or proximate steps in organ systems.

h.     Not reversible

i.       No buffer

There are easily 9 possible answers, 5 marks for any 5 of these.

Marked by Prof Burns

7. (7 marks) Explain what “Automation Complacency” is.  Describe its effect on human operators.  Give an example of automation complacency from the film “Why Planes Crash”.

 

From the notes, automation complacency refers to a situation where operators overtrust the automation.  (1 mark)

They fail to monitor it vigilantly enough,  less active / end of the loop

become less aware of the state of the system

they are slower to detect problems

and less able to intervene in a problem (de-skilling) (4 marks)

An example from the film is when the pilots focus on the burned out lightbulb.  They assume the plane is in autopilot and stop monitoring the altitude.  By the time they realize the plane has descended too much they are unable to intervene.  (2 marks)

Marked by Prof Burns

 

Total marks = 52

Previously seen questions = 29/52=56%

New questions that are very close to old questions = 13/52=25%

Completely new questions = 10/52 = 19%