copyright 2003 by dr. gallimore, wright state university department of biomedical, industrial...
TRANSCRIPT
Copyright 2003 by Dr. Gallimore, Wright State University
Department of Biomedical, Industrial Engineering & Human Factors Engineering
Task Analysis
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
What is Task Analysis?
The study of what an operator (or team of operators) is required to do, in terms of actions and/or cognitive processes, to achieve a system goal. It provides the user with a “blueprint” of human involvement in a system.
Reference: Kirwan, B. and Ainsworth, L.K. (1992. A Guide to Task Analysis Bristol, PA: Taylor & Francis Inc.
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Why Conduct Task Analyses?• Ensure system safety through hazard identification,
effective system design, human reliability assessment, and incident investigation
• Enhance productivity through determination of where to automate system processes, evaluation of staffing and training requirements, and identification of error potential
• Increase system availability by identification of maintenance demands, and requirements for maintenance support tools
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
When Is Task Analysis Done?
• In System DesignThroughout the life-cycle or the system: from initial
concept development, through design, to construction, commissioning, and operation (also in system decommissioning)
• In System EvaluationTo assess impact when system changes, or as part of
periodic reviews (audits or risk assessments)
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Task Analysis Application Areas
• Allocation of functionAllocating functions between personnel and machines,
and defining extent of operator involvement in the control of the system
• Person specificationDefining characteristics and capability requirements of
personnel to enable to efficiently carry out the task
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Task Analysis Application Areas cont.
• Staffing and job organizationDefining the number of staff required, the organization
of team members, communications requirements, and allocation of responsibility
• Task and interface designEnsuring adequate availability and design of information
displays, controls, and tools to enable the operator(s) to adequately carry out the task
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Task Analysis Application Areas cont.
• Skills and knowledge acquisitionTraining and procedures design
• Performance assuranceAssessment of performance predicatively via human
reliability assessment, retrospectively via incident investigation or analysis, or concurrently via problem investigations
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Task Analysis and System Life-Cycle
Human Factors Issue
Concept Spec.
System Def. Design Deploy Ops and Maint
Allocation of function
Best Poss Poss Check
Person specification
Review Check
Staffing Too soon Best Poss Check
Task and interface design
Too soon Best Best
Skills acquisition
Too soon Too soon Best Best Check
Performance assurance
Constantly
From Kirwan and Ainsworth, 1992
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Task Analysis Techniques - Overview
Category Description
Task data collection techniques
Primarily used for collecting data on human- machine interactions, and which then feed into other techniques
Task description techniques
Structure collected information into systematic format. Formats may then serve either as reference material to enhance understanding of human –
machine involvement
Task simulation methods
Aim at compiling data on human involvement to create a dynamic model of task execution. Provides generic model of task performance (in time and
accuracy) based on individual task data
Task behavior assessment
methods
Identify what can go wrong that can lead to system failure, and often deal with hardware, software, and environmental events as well as human errors.
Derived from engineering risk assessment domains
Task requirement evaluation methods
Assess adequacy of facilities which operator(s) have available to support task execution, and directly assess the interface and facilitator designs (e.g.
training manuals)
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Analysis Procedures
• Mission Analysis Function Determination
• Function Allocation
• Task Description / Identification
• Task Analysis
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Mission Analysis (System Requirements Analysis)
• What is the system supposed to accomplish?• The analyst/designer needs to know -
– Specific Goals– Required Outputs– Required Inputs– System Capacities and Performance Requirements– Operating Environmental Factors– Constraints on System Operation
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Mission Analysis Tools
• Mission Profile – Graphic Description (Example - Flight Profile)
• Mission Scenario– Verbal Description - Summarizes typical assumptions, environments, operations.
• Mission Segment– Time period of coherent activities with definite beginning and ending points.
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Importance of Function & Task Analyses
Evaluate Human Factors Implications Design Requirements and ConstraintsWorkload Implications• Notes:1. Decompose to level where functions to be performed by system can be identified.2. Be careful that proposed design solution does not appear to be a function
description.
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Determination of Functions•
Identify and Describe Functions - byDetermining Function Inputs and Outputs
Establishing Functional Performance Criteria
Preparing Functional Flow Diagrams
Function Examples:To Detect To RepairTo Analyze
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Determination of Functions
Functions - Can beInstantaneous (Start Engine)Prolonged( Monitor Radar Screen)Complex (Analyze Equipment
Malfunction)
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Function Performance Criteria
• Yardstick used to measure/predict whether or not the system/function meets the performance requirements.
• Criteria can range from gross to finely detailed.• Functional Performance Criteria must be stated in terms of those test results that must
be satisfied in order for the system/function to meet the performance requirements.• Provides the basis for preparing the Functional Flow Diagram.
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Functional Flow Diagram
• Determine the functions that have already been allocated.• Describe the various different ways that each unallocated function might be
accomplished.• Establish the weighting criteria for comparing the alternatives.• Compare each of the alternative against one another.• Select the most cost-effective design.
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Task Description / Identification
•
• Examine each selected design alternative.
• List in sequence all the actions that must be performed to accomplish the functional element.
• Categorize actions in terms of whether they areoperator or maintainer activities; and by thehardware/software subsystems to which they belong.
• Describe each action in terms of a behavioral verb (see next slide).
• Break tasks down into subordinate tasks by specifying inputs and outputsfor each task/subtask.
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Behavioral Verbs
• ActionExample - to turn on, to monitor, to disassemble
• Equipment Acted UponExample - switch, motor, display
• Consequence of ActionExample - voltage display stabilized
• Stimulus that Initiates the ActionExample - pilot’s command
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Behavioral Verbs (cont)
• Feedback Information Resulting form Task Performance
Example - aircraft heading 320 degrees
• Criterion of task accomplishmentExample - vehicle stopped/parked with 3 feet of
marker
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Task Analysis
• Collect Information (See Table 1 Handouts)• Record Data (See Table 2, Figure 1 Handouts)• Analyze Data (See Table 3 Handouts)
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Task Analysis Techniques
• Task Data Collection Methods– Activity sampling– Critical incident technique– Observational techniques– Questionnaires– Structured interviews– Verbal protocols
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Task Analysis Techniques cont.
• Task description methods (charting and network)– Input-output diagrams– Process charts– Function flow diagrams– Information flow charts– Critical path analysis– Petri nets– Signal flow graphs
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Task Analysis Techniques cont.
• Task requirements evaluation methods– Ergonomics checklists– Interface surveys
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Task Analysis Techniques cont.
• Task description methods– Hierarchical task analysis– Link analysis– Operational sequence diagrams– Timeline analysis
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Task Analysis Techniques cont.
• Task behavior assessment methods– Barrier and work safety analysis– Event trees– Failure modes and effects analysis– Fault trees– Hazard and operability analysis– Influence diagrams– Management oversight risk tree technique
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Task Analysis Techniques cont.
• Task simulation methods– Computer modeling and simulation– Simulators and mock-ups– Table-top analysis– Walk-through and talk-through
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
HTA – A General-Purpose Task Analysis Technique
• Hierarchical Task Analysis (HTA)– Developed for use in training domain (Annett et al.,
1971)– Requires the analyst to establish conditions when
various subtasks should be carried out to meet a system’s goals
– Produces a hierarchy of operations and plans– Activities of human operator are linked directly to
system requirements
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
HTA Application
• For all stages of system life-cycle• Used to deal with:
– Interface design– Work organization– Facilitator design– Human error analysis
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Basic Terms
• GoalsDesired states of systems under human control or supervision
• TasksMethods adopted to attain the goal, in any instance, which is
constrained by: availability and cost of materials; equipment and facilities demands; availability and cost of services; time constraints; legal obligations; and personnel preferences
• OperationsAny unit of behavior, no matter how long or short in duration, and no
matter how simple or complex in structure, which can be defined in terms of its objective
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Basic Concepts
• Hierarchies of goals and sub-goalsGoals can be described at various levels of detail, thereby allowing
the nesting of goals (sub-goals)
• Plans and the organization of sub-goalsPlans specify condition when sub-goals should be carried out. Can
include sequences of actions or sets of actions conditional upon time or events
• Stopping rulesStop converting goals into plans and sub-operations when effort and
time is no longer justified. The rule may depend on the domain or particular task
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Task AnalysisExample of Question Categories
• Design Questions• Manning Questions• Training Questions• Test and Evaluation Questions
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Design Questions
• What tasks need to be performed?
• How critical is each task?
• In what sequence must the tasks be performed?
• What control activations are required?etc, etc, etc, etc
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Manning Questions
• How many people are required to perform the task?
• What skill levels are required?
Department of Biomedical, Human Factors, & Industrial Engineering
Copyright 2001 by Dr. Gallimore, Wright State University
Training Questions
• On what behavioral dimensions are the tasks performed?
• How difficult or complex is each task?
• What information is required to perform the task?etc, etc, etc, etc