Presentation on theme: "Tutorial 4: Case Study “Set Phasers on Stun” SY DE 142 – June 7, 2004"— Presentation transcript:
1 Tutorial 4: Case Study “Set Phasers on Stun” SY DE 142 – June 7, 2004 Introduction to Human Systems EngineeringWaterloo, Ontario, Canada
2 Outline Case Study: “Set Phasers On Stun” Discussion on “Set Phasers on Stun”Midterm Overview
3 Set Phasers on Stun Overview Time: 1986Place: East Texas Cancer Center, TylerSynopsis: A computer glitch turns miracle machine into monster for one cancer patient. Mode error combine with lack of feedback deliver a blast of 25,000 rads down onto the patient.
4 Set Phasers on Stun Interface Design Draw out the general Human machine system model and redraw it for this case.What feedback was available to Mary Beth and what was missing?
5 Set Phasers on Stun “Information Displays” a: mary beth's commandb: control signalc: raysd: patient statee: feedback on Therac state and actionsf: feedback on interface state and actions(control signal sent)g: interface informationHuman = Mary Beth -Interface = Therac Control PanelMachine = TheracWorld = Patient
6 Set Phasers on Stun Feedback Mary Beth needed to know:the control signal was sentthe Therac modethat the Therac had sent out rayspatient state.14 marks: 5 for the draw, 5 for redraw and 4 for feedback
7 Midteram Overview SY DE 142 Midterm: Room: DC 1350 Date: June 14, 2004 Time: 1:30 - 3:30pmRoom: DC 1350Aids Allowed:Text book: Wickens and Set Phasers on StunCalculatorSolutions must be written in pen, not in pencil.
8 Case Studies Business in Bhopal Silent Warning In Search of the Lost CordAn Act of GodThe Wizards of Wall StreetSet Phasers on Stun
9 Films Death on the Job Bhopal, a Lingering Tragedy Why Planes Crash Broken Bus
10 Course Material Outline Accident Analysis and Fault TreesMappings and AffordancesGulfs of Execution and EvaluationHuman Action CycleInformation ProcessingHuman Decision MakingHuman Error - MistakesHuman Error- slipsHuman machine modelDisplaysControlHuman-Computer InteractionUsability TestingAutomationMore details on slides and in book.
11 Accident Analysis and Fault Trees Linear interactionsCommon mode interactionNonlinear interactionsTight vs. Loose couplingFMECAFault Tree AnalysisChronologicalShow causalityEvents: action and time (time often implicit)AND/OR gatesLast event at the topORAND
12 Mappings and Affordances Mapping : relation between action and its result in the worldHelps automatic processing when extremely strong between world and required actionTwo kinds; natural (steering wheel), social/cultural (light switch)Affordance:perceived and actual properties of things that help to direct users’ actions, should be applied as a design principal“Affordances become visible by establishing mappings, (what it does, how it works)”
13 Gulfs of Execution and Evaluation (and HAC) Execution: have an intention but can’t figure out action (difference in seq of action & action in the Human Action Cycle)Evaluation: Can’t figure out whether the goal has been achieved
14 HUMAN ACTION CYCLE GOAL Intention Evaluate Act Evaluate Sequence of Actions (what should be done)Gulf of evaluation!InterpretGulf of execution!PerceptionHow is state of the world perceived? Use sensesAct!WORLDInterpret
15 Information Processing “How we Think” MemoryShort term, long term , how to improve, knowledge in head vs. knowledge in worldPerceptionFeature analysis (bottom-up processing), unitization, top down processing ----design implicationsAttentionSelective, divided design implicationsResource model, Multiple resource model
16 More Information Processing “How we Think” Situation awareness (SA): being aware of meanings of dynamic changes in the environment3 stages: Perceive, understand, predictMeasuring SA: by SA Global Assessment technique (SAGAT)Decision makingNormative model (methods: multi-attribute utility theory, expected value theory, SEUT)Descriptive model (methods: satisfaction not optimal, heuristics, and biases to create easier ways of thinking)
17 Human Decision MakingHeuristics and Biases in Human decision making (look at updated lecture notes)could happen in any of the following stages:1. Getting information input (input or cue biases)2. Generating hypotheses and selection ( 6 biases).3. Plan generation and action choice (4 biases).SRK FrameworkSkill based decisions (automated)Rule Based decisions (procedural)Knowledge based decisions
18 Human Error -- mistakeMistake: wrong goal and intention but right actionWhy it happens?Types of mistakemistaken similarity,misjudged probability,rationalizing small events,social pressures/cultural factors and $Forcing Functions
19 Human Error -- slips Slip: right goal and intention but wrong action, Mostly occurs with skilled behavior (WHY?)Mode Error: right action in wrong mode (therefore the action becomes WRONG)
20 Information Displays Human-Machine Model Human machine system model :Elements:user Interface machine Worldbegins with Action :Operator acts on the interface.Interface sends a control signal to the machine.Machine acts on the world.Feedback: (4 feedbacks)State of world to interfaceAction of machine to interfaceIndication of control signal (machine to interface)Information from interface to operatorAny missing item may cause an accident
21 Display contents should permit evaluation and execution Display principles:Perceptual (legible, give reference, redundancy, design for distinctive features)Mental model (pictorial, moving part, ecological)Attention (multi-resource, proximity compatibility, information access cost)Memory (predictive aids, knowledge in the world, consistency
22 Display forms Digital vs. Analog (precision vs. change) Configural displaysRankine cyclePolar star displayHeads-upEcological displays
23 ControlControl vs. display : control is same as display till user interacts with system through displayVery important in design same guidelines as displays.Laws and principals:Hick-Hyman law for Reaction TimeFitts law for Movement TimeControl Types : zero order (mouse), first order (steering wheel) and second order (thrust of shuttle)
24 Human-Computer Interaction What your focus is as a designer:User group:who is using your system (novice, infrequent, frequent expert) and what should you know about these users.Interaction styles:how will the user (based on expertise) interact with the system (eg. Menu, form, QA, command language, function keys, direct manipulation, natural language, ….)
25 Usability and user testing Usability Approaches (4)Cognitive walkthroughHeuristic evaluation (Neilson’s usability principals)Performance measurementField studyTasksUsability measures (satisfaction, learnability, errors)
26 Automation When and why use automation Classes of automation Information acquisition (warnings, filters)Information integration (pattern recognition, expert systems)Action selection (TCAS)Action execution and control (autopilots, cruise control)
27 Automation Levels of automation Reliability Issues: complacency (over trust),mistrust,dumb and dutiful effect.Best form is Human Centered Automation
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