Usability Engineering

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Usability Engineering

• Dr. Dania Bilal
• IS 582
• Spring 2006

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What Is Usability Engineering?

• Measures multiple components of the user
  interface
• Addresses the relationships between system and
  its users
• Focuses on the HCI field

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What Is Usability Engineering?

• Bridges the gap between human and machines
• Measures the quality of a system in relation to
  its intended users
• Involves several methods, each applied at
  appropriate time of the design and development
  process

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Importance of Usability

• The sooner problems are found, the less expensive
  it is to fix them
• Saves money by reducing designers and
  developers time

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Importance of Usability

• Learn more about users, tasks, expectations,
  successes, failures, information seeking, etc.
  and take these into consideration in redesigning
  a system or designing new one

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Usability Attributes

• As described by Neilsen
• Learnability
• Efficiency
• Memorability
• Errors their severity
• Subjective satisfaction

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Learnability

• The system must be easy to learn, especially for
  novice users.
• Hard to learn systems are usually designed for
  expert users.
• There is a learning curve for novice and expert
  users.

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Efficiency

• The system should be efficient to use so that
  once the user has learned how to use it, the user
  can achieve a high level of productivity.
• Efficiency increases with learning

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Memorability

• The system should be easy to remember, especially
  by casual users, so that they do not have to
  learn it all over again after a period of not
  using it.

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Errors

• The system should have a low error rate and
  should provide the user with a recovery mechanism
  from errors.
• Minor errors
• Major errors

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Minor Errors

• User was able to recover from them
• through system feedback
• through awareness of error made
• Errors that did not greatly slow down the users
  interaction with the system

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Major Errors

• Difficult to recover from them
• Lead to faulty work especially if they are high
  in frequency
• May not be discovered by the user
• These errors can be catastrophic

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Subjective Satisfaction

• The system should be likeable by users
• Satisfaction varies with kind of system used
  (educational vs. entertainment)

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Assumptions

• The designers best guess is not good enough
• The user is always right
• The user is not always right
• Users are not designers
• Designers are not users
• More features are not always better
• Minor interface details matter
• Online help does not really help
• Source Nielsen, J. (1993). Usability
  Engineering. San Diego Morgan Kaufman.

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Factors

• Address the functionality of the system
  vis-à-vis
• user needs
• user tasks
• user information seeking
• user expectations
• user cognitive processes

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Usability Testing

• Part of the process of usability engineering
• Involves users in the evaluation of a system by
  testing it
• Goal
• Uncover problems and correct them

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Usability Evaluation

• Conducted at many stages during and after the
  system design process.
• Employs various methods

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Methods

• Cognitive walkthrough
• Focus groups
• Prototyping
• Task analysis
• Inspection
• User testing
• http//www.usabilityfirst.com/methods

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Usability Heuristics

• http//www.useit.com/papers/heuristic/heuristic_li
  st.html for usability principles
• http//www.useit.com/papers/heuristic/heuristic_ev
  aluation.html for how to conduct a heuristic
  evaluation
• http//www.uie.com/articles

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Usability Tests

• Stages
• Preparation
• Introduction
• Test itself
• Debriefing
• Neilsen, J. (1993). Usability Engineering. San
  Diego Morgan Kaufman.

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Preparation

• Preparation for the experiment and data
  collection
• Location of test (e.g., room to be used)
• System to be used, capturing software, etc.
• Test materials, instructions, questionnaires to
  be completed, as applicable

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Introduction

• Test introduction includes
• Purpose of the test
• Test results to be used to improve interface
• Confidentiality of results IRB
• Explanation of software and equipment used to
  collect data

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Introduction

• Users to ask clarifying questions anytime before
  and during the experiment
• Users to report problems and difficulty in using
  system during experiment (e.g., screen freeze)
• Verbal instructions, as applicable Introduction

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Running the Test

• Experimenter(s) should refrain from interacting
  with users (e.g., personal opinions should not be
  expressed)
• Experimenter(s) guide(s) observers. Both groups
  should refrain from making obtrusive comments
  during the experiment

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Debriefing

• User is debriefed after the test and may be asked
  to make comments or suggestions
• verbally (via individual interview)
• by completing a questionnaire

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Debriefing

• Experimenter ensures that files are collected
  with correct labeling checks captured data
  files, questionnaires, etc.
• Experimenter may write a brief preliminary report
  while events are still fresh.