Task Analysis: HTA

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Task Analysis HTA

• Ainsworth, Les Marshall, Ed (1998)
• Shepard, A. (1998)

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Definition of Task

• Shepard argues that task is insufficiently
  defined in many papers
• Offers the following a task is a problem
  facing an operator
• Therefore, task analysis is a method serving to
  identify strategies by which the operator can be
  facilitated to solve the problem.

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So whats an HTA?

• Hierarchical Task Analysis
• Method or Strategy of cutting up Tasks into
  ordered sub-tasks aimed at refining performance
  criteria, focussing on constituent skills,
  understanding task contexts and generating useful
  hypotheses for overcoming performance problems

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Where is HTA useful?

• HTA was not typically used for cognitive task
  assesment, but Shepards paper disagrees
• Historically, HTA was used for behaviors only,
  defined as what they do only
• Its output is a record of a process, so it
  should be useful anywhere you have a process

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HTA Framework
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• Set Goals performance problems, improvement,
  etc. critical incident technique (Flanagan
  1954)
• Observe Constraints mgmt limitations,
  environment, etc.
• Criticality P X C rule (Annett Duncan 1967)
• Cease Redescription
• Generate Hypothesis How to fix or improve
• Cost/Benefit Does the fixs cost outweigh its
  benefit?
• Record Analysis Use graphs, tables, etc.
• Redescription More detail may be necessary
• Challenge Constraints too restrictive to be
  beneficial?

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Adding CTA into the Process

• CTA Cognitive Task Analysis
• Cognition is present when you have supervision,
  control of complex systems, human-computer
  interaction
• CTA tries to capturethe knowledge that people
  have, or needin order to complete a task
  Preece et al. (1994)
• Many state CTA ? HTA

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Knit-picky, huh?

• Granted, some things can be mindless, but
  thinking has to come into play at some point in
  ANY process.
• Cognitive tasks do need some emphasis within the
  HTA framework ?

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• Goal context the guy holding the flag will react
  differently than the guy responsible for the
  whole project, even if performing the same task
• Frequency, Predictability Coincidence Stated
  in HTA plans
• Priming Think Pavlov
• Decision Outcome often there many choices
• Criticality ditto to HTA
• Evaluating Cognitive skill evaluate CTA insights
  (problem hypothesis, design hypothesis)

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HTA in use

• Ainsworth Marshall compared multiple studies in
  the UK nuclear defense industries
• Most involved high level cognitive skills in
  time-critical situations
• Preferred over simply following established
  written procedures
• Many important points were noted ?

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Data Sources

• MUST be clearly defined. Many studies did a poor
  job of this. Examples
• completely omitting references or inadequately
  defining them
• not defining experience levels of experts
• omitting key details (simulators v. systems)

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Data Collection Analysis

• HTA plans need to be more developed
• Do not rely too heavily on workload analysis
• More guidance needed in proper graphical
  techniques (overly complicated or trivial)
• Walk-throughs informal discussions seemed to be
  best, questionnaires structured interviews
  worst
• Critical incidents need to be sought reported

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Data Presentation

• Analysts need to be clearly identified
• Thoroughness of walk-throughs other on-site
  evaluations need to be declared
• Experts need to have their credentials stated
• Task timing methods need to be reported

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Task Decomposition

• Make formalized Task Decomposition tables
• Make them DETAILED
• (the more TD in the studies yielded more detailed
  design recommendations in both industries)

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HTA Alternative

• Timelines were the most widely used alternatives
  in the studies.
• They provide good measure of feasibility
• Beware - the scale of the timeline is often
  difficult to assess and therefore may be
  presented poorly

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Final Notes

• Objectives should be defined early on by those
  commissioning the TA, with help from analysts
• HF experienced analysts will typically provide
  more insightful recommendations
• Depth of analysis should be clearly stated
• Resources required for the TA should be stated
• Any lastly ?

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