Task Analysis.ppt

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1、Department of Biomedical, Industrial Engineering & Human Factors Engineering,Task Analysis,Department of Biomedical, Human Factors, & Industrial Engineering,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,

2、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,Why Conduct Task Analyses

3、?,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 pote

4、ntial Increase system availability by identification of maintenance demands, and requirements for maintenance support tools,Department of Biomedical, Human Factors, & Industrial Engineering,When Is Task Analysis Done?,In System Design Throughout the life-cycle or the system: from initial concept dev

5、elopment, through design, to construction, commissioning, and operation (also in system decommissioning) In System Evaluation To assess impact when system changes, or as part of periodic reviews (audits or risk assessments),Department of Biomedical, Human Factors, & Industrial Engineering,Task Analy

6、sis Application Areas,Allocation of function Allocating functions between personnel and machines, and defining extent of operator involvement in the control of the system Person specification Defining characteristics and capability requirements of personnel to enable to efficiently carry out the tas

7、k,Department of Biomedical, Human Factors, & Industrial Engineering,Task Analysis Application Areas cont.,Staffing and job organization Defining the number of staff required, the organization of team members, communications requirements, and allocation of responsibility Task and interface design Ens

8、uring 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,Task Analysis Application Areas cont.,Skills and knowledge acquisition Training and procedu

9、res designPerformance assurance Assessment 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,Task Analysis and System Life

10、-Cycle,From Kirwan and Ainsworth, 1992,Department of Biomedical, Human Factors, & Industrial Engineering,Task Analysis Techniques - Overview,Department of Biomedical, Human Factors, & Industrial Engineering,Analysis Procedures,Mission Analysis Function DeterminationFunction AllocationTask Descriptio

11、n / IdentificationTask Analysis,Department of Biomedical, Human Factors, & Industrial Engineering,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 Perf

12、ormance Requirements Operating Environmental Factors Constraints on System Operation,Department of Biomedical, Human Factors, & Industrial Engineering,Mission Analysis Tools,Mission Profile Graphic Description (Example - Flight Profile) Mission Scenario Verbal Description - Summarizes typical assump

13、tions, environments, operations. Mission Segment Time period of coherent activities with definite beginning and ending points.,Department of Biomedical, Human Factors, & Industrial Engineering,Importance of Function & Task Analyses,Evaluate Human Factors Implications Design Requirements and Constrai

14、nts Workload 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,Determination of Functions,I

15、dentify and Describe Functions - byDetermining Function Inputs and OutputsEstablishing Functional Performance CriteriaPreparing Functional Flow DiagramsFunction Examples:To Detect To RepairTo Analyze,Department of Biomedical, Human Factors, & Industrial Engineering,Determination of Functions,Functio

16、ns - Can beInstantaneous (Start Engine)Prolonged ( Monitor Radar Screen)Complex (Analyze Equipment Malfunction),Department of Biomedical, Human Factors, & Industrial Engineering,Function Performance Criteria,Yardstick used to measure/predict whether or not the system/function meets the performance r

17、equirements. 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.,Dep

18、artment of Biomedical, Human Factors, & Industrial Engineering,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.

19、Compare each of the alternative against one another. Select the most cost-effective design.,Department of Biomedical, Human Factors, & Industrial Engineering,Task Description / Identification,Examine each selected design alternative. List in sequence all the actions that must be performed to accompl

20、ish the functional element. Categorize actions in terms of whether they are operator or maintainer activities; and by the hardware/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 inpu

21、ts and outputs for each task/subtask.,Department of Biomedical, Human Factors, & Industrial Engineering,Behavioral Verbs,Action Example - to turn on, to monitor, to disassemble Equipment Acted Upon Example - switch, motor, displayConsequence of Action Example - voltage display stabilizedStimulus tha

22、t Initiates the Action Example - pilots command,Department of Biomedical, Human Factors, & Industrial Engineering,Behavioral Verbs (cont),Feedback Information Resulting form Task Performance Example - aircraft heading 320 degreesCriterion of task accomplishment Example - vehicle stopped/parked with

23、3 feet of marker,Department of Biomedical, Human Factors, & Industrial Engineering,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,Task Analysis

24、 Techniques,Task Data Collection Methods Activity sampling Critical incident technique Observational techniques Questionnaires Structured interviews Verbal protocols,Department of Biomedical, Human Factors, & Industrial Engineering,Task Analysis Techniques cont.,Task description methods (charting an

25、d 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,Task Analysis Techniques cont.,Task requirements evaluation methods Ergonomics checkli

26、sts Interface surveys,Department of Biomedical, Human Factors, & Industrial Engineering,Task Analysis Techniques cont.,Task description methods Hierarchical task analysis Link analysis Operational sequence diagrams Timeline analysis,Department of Biomedical, Human Factors, & Industrial Engineering,T

27、ask 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

28、 Engineering,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,HTA A General-Purpose Task Analysis Technique,Hierarchical T

29、ask 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 systems goals Produces a hierarchy of operations and plans Activities of human operator are linked directly to system requi

30、rements,Department of Biomedical, Human Factors, & Industrial Engineering,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,Basic Terms,Go

31、als Desired states of systems under human control or supervision Tasks Methods 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 perso

32、nnel preferences Operations Any 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,Basic Concepts,Hierarchies of goals and sub-go

33、als Goals can be described at various levels of detail, thereby allowing the nesting of goals (sub-goals) Plans and the organization of sub-goals Plans specify condition when sub-goals should be carried out. Can include sequences of actions or sets of actions conditional upon time or events Stopping

34、 rules Stop 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,Task Analysis Example of Question Categories,Design Questions Manning Questio

35、ns Training Questions Test and Evaluation Questions,Department of Biomedical, Human Factors, & Industrial Engineering,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,D

36、epartment of Biomedical, Human Factors, & Industrial Engineering,Manning Questions,How many people are required to perform the task? What skill levels are required?,Department of Biomedical, Human Factors, & Industrial Engineering,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,Department of Biomedical, Human Factors, & Industrial Engineering,Test and Evaluation Questions,What are the performance criteria for the task or job?,