Detailed Task Analysis and Failure Modes and Effects Analysis
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 2
Task Analysis High-Level Task Analysis ● – Hierarchical Task Analysis (HTA) ≈ IDEF0 Nodelist – Functional Flow Charts – Functional Analysis/Modeling = Activity Analysis/Modeling = Process Analysis/Modeling We 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 3
Task Analysis High-Level Task Analysis ● – Hierarchical Task Analysis (HTA) ≈ IDEF0 Nodelist – Functional Flow Charts – Functional Analysis/Modeling = Activity Analysis/Modeling = Process Analysis/Modeling We 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 4
Hierarchical Task Analysis of Cesarean Delivery Process (original version, in “org chart” format) 5
Hierarchical Task Analysis of Cesarean Delivery Process (current IDEF0 nodelist version) 6
Task Analysis High-Level Task Analysis ● – Hierarchical Task Analysis (HTA) ≈ IDEF0 Nodelist – Functional Flow Charts (handout) – Functional Analysis/Modeling = Activity Analysis/Modeling = Process Analysis/Modeling We 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 7
Functional Flow Charts 8
Task Analysis High-Level Task Analysis ● – Hierarchical Task Analysis (HTA) ≈ IDEF0 Nodelist – Functional Flow Charts (handout) – Functional Analysis/Modeling = Activity Analysis/Modeling = Process Analysis/Modeling We 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 9
Part of ECD High-Level Task Analysis (IDEF0 A3 diagram) 10
Task Analysis High-Level Task Analysis ● – Hierarchical Task Analysis (HTA) ≈ IDEF0 Nodelist – Functional Flow Charts (handout) – Functional Analysis/Modeling = Activity Analysis/Modeling = Process Analysis/Modeling We 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 11
ECD Detailed Task Analysis Tasks (leaf nodes) selected for DTA 12
ECD Detailed Task Analysis 13
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 decision aids, other JPAs operator makes to perform tasks Actions Actions operator needs to perform task controls, tools Frequency & Duration How often, how long automation, seating, supports, ... Environmental Conditions Illumination, temperature, vibration, lighting, clothing, ... noise, acceleration, ... Potential Errors, Risks Omissions, commissions, mistakes, JPAs, other slips, … Risk level based on frequency, countermeasures consequences, detectability Remarks/Comments Additional useful info to aid TA others (optional) see handout 14
ECD Detailed Task Analysis 15
Questions for Detailed Task Analysis Source: Chapanis, A. (1996). Human Factors In Systems Engineering. New York: John Wiley & Sons, Inc., p. 107. 16
Some Sensory / Cognitive / Motor Action Verbs (useful in Decision/Action TA fields) Attend to Configure ● ● Detect Disengage ● ● Distinguish between Engage ● ● Feel Grasp ● ● Hear Manipulate ● ● Read Move ● ● View Open ● ● Remember Pick up ● ● Calculate Position ● ● Count Press ● ● Decide among Reach to ● ● Estimate Reach to ● ● Evaluate Release ● ● Generate Transfer ● ● Predict Turn ● ● Process Wait for ● ● Walk to ● 17
Supplementary Information for Detailed Task Analysis See handouts ● 18
Failure Modes and Effects Analysis (FMEA) 19
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 20
Example FMEA (from electronics inspection/repair workstation design project) 21
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. negligible 2. minor 3. moderate 4. major 5. catastrophic 22
FMEA Fields (2) Probability ● – Numeric rating of the estimated probability that the failure will occur, e.g., 1. Remote 2. Unlikely 3. Occasional 4. Common 5. Frequent 23
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 high 3.Should the failure occur there is a high probability that the existing controls will detect it. 4.Moderately high 5.Existing controls have difficulty detecting the failure 6.Low 7.Controls are weak. Detection could depend on a lucky catch. 8.Remote 9.Very remote 10.No controls for this failure mode exist RPN: Risk Priority Number ● – RPN = Probability x Severity x Non-detectability 24
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). 25
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