COMP386 Human Computer Interaction by rtu18834

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									COMP287: Human Computer Interaction                                    Example Exam
Total marks: 100

SOLUTIONS

Question 1 [24 marks]
a) Comment on the definition: 'HCI is about the way computer technology
    affects people'. [8 marks]
Generally correct but too broad
Emphasis in HCI is on software
Includes interface and functionality of software in supporting user tasks
May miss the fact that software is not just in ‘computers’ but also household items
such as video recorders.

b) What is meant by the term 'gulf of execution' in using an interactive system
    and why is it important? [8 marks]
Translation from ‘what the user intends to do’ to ‘what actions need to be performed
at the interface’. Is a potential problem in the interaction cycle and a poor mapping
(difficult translation) leads to poor usability.


c) Describe the different aspects affecting the learnability of interactive systems,
   giving examples where appropriate. [8 marks]
Predictability – easy for user to reason from experience to accurate predictions of the
effect and availability of operations. Eg. If there is a tool for drawing ellipses, there
will be a tool for drawing rectangles.
Synthesisability – easy for user to build accurate mental model of the way the system
works.
Familiarity – similar to other systems known by user. Eg. Save function in ‘File’
menu.
Generalisability Easy for user to reason from specifics of operations to accurate
general rules. Eg. Use ellipse tool to draw circle therefore use rectangle tool to draw
squares.
Consistency – similar things done in similar ways.
Question 2 [12 marks]
Write a Hierarchical Task Analysis description for ‘eating at a restaurant’. The
description should contain enough detail to illustrate the main features of the
technique.
0. eating at a restaurant
    1. find table
    2. select entrée, main course and drink
    3. eat entrée
    4. eat main course
    5. select dessert
    6. eat dessert
    7. pay
    8. leave

7.1       attract waiter’s attention
7.2       ask for bill
7.3       check bill
7.4       pay
7.5       wait for change
7.6       leave tip

plan 0:
          do 1
          after receiving menu do 2
          after receiving entrée do 3
          after receiving main course do 4
          if desired do 5 and then 6
          do 7 and then 8

plan 7:
          do 7.1 - 7.4
          if necessary do 7.5
          if good service do 7.6
Question 3 [24 marks]
a) Explain what is meant by the term ‘heuristic evaluation’. [8 marks]
Heuristic evaluation is a structured form of expert review which emphasises general
usability issues rather than the particular tasks of users. It is a cost-effective method
suitable for smaller companies. The design inspection is guided by high-level
heuristics focussing on key usability issues of concern, eg.:
consistency
feedback
speaking the users’ language

b) What are the advantages and disadvantages of 'interpretive evaluation' as
     compared with experimental techniques? [8 marks]
Advantages:
Criticisms of experimental techniques are that they are 'artificial' since they remove
the user from the natural work environment in one way or another and that they are
not really objective anyway since even numbers must be interpreted. The emphasis in
interpretive evaluation is on the usefulness of the findings for the people concerned
(ie. the users).
Disadvantages:
Not objective / repeatable / quantifiable
Require high degree of expertise
Time consuming

c) Give an example of an independent variable and a dependent variable in a
    usability experiment. [8 marks]
Independent variable: Depth of menus
Dependent variable: Time required for user to perform benchmark tasks requiring use
of menus.



Question 4 [24 marks]
a) What is meant by the term 'task allocation'? Give an example. [8 marks]
Decision of which parts of a task are performed by the software and which parts are
performed by the user. Example: a word-processor does automatic spell-checking but
checks with the user on the action to be taken when it finds a word that is not in its
dictionary.
b) What are the similarities and difference between the ‘spiral model’ and the
    ‘star model’ in software design? [8 marks]
Similarities:
Both try to solve the problems of the waterfall model.
Both try to discover problems early.
Both are iterative approaches
Both depend on prototyping and feedback from stakeholders
Differences:
Spiral model repeats SD-phases in a fixed order with more and more complete
prototypes and evaluation only after implementation.
Star model has evaluation as central concept at all phases. No fixed sequence of
phases. More flexible, potentially less costly but requires more experience. Developed
especially for user-centred design.

c) What is meant by a ‘master-slave’ architecture in implementing a CSCW
   system? What advantage does this have over a ‘client-server’ architecture? [8
   marks]

The application runs on the network node on which it was started (the master). Other
  nodes (slaves) use this as a server. In contrast to ‘client-server’, the application
  does not run on the same special server node each time it is started.
This provides good performance and rapid feedback for a user at the node acting as
  master. If the application is often used by only one user at a time, this may be
  much better than ‘client-server’.


Question 5 [16 marks]
Write a VBA procedure which sets the width of a CommandButton to the value
entered in a TextBox. Check that the value is a valid, positive numeric value less
than 1000 and, if it is not, write an error message to a label field called
‘errorlabel’. The CommandButton and TextBox to be used by the procedure
should be parameters of the procedure.
private sub setWidth(cb as CommandButton, tb as TextBox)
  dim w as Integer
  if isNumeric(tb.text) then
    w=val(tb.text)
    if w>0 and w<1000 then
       cb.width=w
       exit sub
    end if
  end if
  errorlabel.caption=”Invalid button width”
end sub

								
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