Detailed Task Analysisand Failure Modes and Effects Analysis

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HFE Requirements Development

● Sources– Customer– Subject Matter Experts– Users, operators– Existing, similar systems– Brainstorming– Task Analysis

● Goals– Identify requirements– Unverifiable (“Customer”) Requirements

→ Verifiable (“Engineering”) Requirements

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Task Analysis

● High-Level Task Analysis– Hierarchical Task Analysis (HTA) ≈ IDEF0 Nodelist– Functional Flow Charts– Functional Analysis/Modeling

= Activity Analysis/Modeling= Process Analysis/ModelingWe do this with IDEF0.

– other methods● Low-Level Task Analysis

– Detailed Task Analysis (used in IE 545)– GOMS (Goals, Operators, Methods, Selection rules)– Cognitive Task Analysis (CTA)– other methods

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Task Analysis

● High-Level Task Analysis– Hierarchical Task Analysis (HTA) ≈ IDEF0 Nodelist– Functional Flow Charts– Functional Analysis/Modeling

= Activity Analysis/Modeling= Process Analysis/ModelingWe do this with IDEF0.

– other methods● Low-Level Task Analysis

– Detailed Task Analysis– GOMS (Goals, Operators, Methods, Selection rules)– Cognitive Task Analysis (CTA)– other methods

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Hierarchical Task Analysis of Cesarean Delivery Process(original version, in “org chart” format)

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Hierarchical Task Analysis of Cesarean Delivery Process(current IDEF0 nodelist version)

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Task Analysis

● High-Level Task Analysis– Hierarchical Task Analysis (HTA) ≈ IDEF0 Nodelist– Functional Flow Charts (handout)– Functional Analysis/Modeling

= Activity Analysis/Modeling= Process Analysis/ModelingWe do this with IDEF0.

– other methods● Low-Level Task Analysis

– Detailed Task Analysis– GOMS (Goals, Operators, Methods, Selection rules)– Cognitive Task Analysis (CTA)– other methods

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Functional Flow Charts

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Task Analysis

● High-Level Task Analysis– Hierarchical Task Analysis (HTA) ≈ IDEF0 Nodelist– Functional Flow Charts (handout)– Functional Analysis/Modeling

= Activity Analysis/Modeling= Process Analysis/ModelingWe do this with IDEF0.

– other methods● Low-Level Task Analysis

– Detailed Task Analysis– GOMS (Goals, Operators, Methods, Selection rules)– Cognitive Task Analysis (CTA)– other methods

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Part of ECD High-Level Task Analysis (IDEF0 A3 diagram)

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Task Analysis

● High-Level Task Analysis– Hierarchical Task Analysis (HTA) ≈ IDEF0 Nodelist– Functional Flow Charts (handout)– Functional Analysis/Modeling

= Activity Analysis/Modeling= Process Analysis/ModelingWe do this with IDEF0.

– other methods● Low-Level Task Analysis

– Detailed Task Analysis– GOMS (Goals, Operators, Methods, Selection rules)– Cognitive Task Analysis (CTA)– other methods

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ECD Detailed Task Analysis

Tasks (leaf nodes) selected for DTA

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ECD Detailed Task Analysis

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Detailed Task Analysis Fields(for IE 545)

Field Description Potential Requirements

Task Name, brief description reminders (task, steps)

Start Cue Event, interval, stimulus that triggers task performance

Information Info operator needs to perform task info to display, visibility, ...

Decision(s) Decisions, evaluations, calculations operator makes to perform tasks

decision aids, other JPAs

Actions Actions operator needs to perform task controls, tools

Frequency & Duration How often, how long automation, seating, supports, ...

Environmental Conditions Illumination, temperature, vibration, noise, acceleration, ...

lighting, clothing, ...

Potential Errors, Risks Omissions, commissions, mistakes, slips, … Risk level based on frequency, consequences, detectability

JPAs, other countermeasures

Remarks/Comments Additional useful info to aid TA

others (optional) see handout

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ECD Detailed Task Analysis

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Questions for Detailed Task AnalysisSource: Chapanis, A. (1996). Human Factors In Systems Engineering. New York: John Wiley & Sons, Inc., p. 107.

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Some Sensory / Cognitive / Motor Action Verbs(useful in Decision/Action TA fields)

● Attend to● Detect● Distinguish between● Feel● Hear● Read● View● Remember● Calculate● Count● Decide among● Estimate● Evaluate● Generate● Predict● Process

● Configure● Disengage● Engage● Grasp● Manipulate● Move● Open● Pick up● Position● Press● Reach to● Reach to● Release● Transfer● Turn● Wait for● Walk to

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Supplementary Information for Detailed Task Analysis

● See handouts

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Failure Modes and Effects Analysis (FMEA)

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Failure Modes and Effects Analysis (FMEA)

● Purpose– Systematically, prospectively, identify ways in which a process

(system) can fail: Failure Modes.– Identify factors potentially contributing to failures.– Estimate risk of failure– Identify countermeasures– Develop requirements

● Method (HMSEM)– Select task on which to perform FMEA (TA should have been

completed on it)– Prepare task FMEA worksheet from [template] worksheet

● copy [template] worksheet● rename new task FMEA worksheet to task's A-number● copy task row from [Summary] worksheet to row 6 of new task FMEA

worksheet● (optionally) hide non-FMEA columns (A-Z)

– Perform FMEA

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Example FMEA(from electronics inspection/repair workstation design project)

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FMEA Fields

● Contributing Factors– Circumstances, conditions, events, factors, ... anything that might

make a failure mode more likely.● Potential Failure Mode

– A way in which the process/system can fail.● Potential Effects of Failure Mode

– Consequences of the failure.● Severity

– Numeric rating of the estimated severity of consequences, of the failure, e.g.,

1. negligible2. minor3. moderate4. major5. catastrophic

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FMEA Fields (2)

● Probability– Numeric rating of the estimated probability that the failure will

occur, e.g.,1. Remote2. Unlikely3. Occasional4. Common5. Frequent

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FMEA Fields (3)

● Non-detectability– Numeric rating of the difficulty of detecting the failure in time to

prevent or mitigate its consequences, e.g.,1.Should the failure occur, there is a virtual certainty that the existing

controls will detect it.2.Very high3.Should the failure occur there is a high probability that the existing

controls will detect it.4.Moderately high5.Existing controls have difficulty detecting the failure6.Low7.Controls are weak. Detection could depend on a lucky catch.8.Remote9.Very remote10.No controls for this failure mode exist

● RPN: Risk Priority Number– RPN = Probability x Severity x Non-detectability

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FMEA Fields (4)

● Potential Remediations– Design strategies that could reduce the likelihood of the failure

mode.● Design Requirements

– Abbreviated requirements statements for remediations.– Requirement numbers (for future reference).