# Shared Flashcard Set

## Details

Human Factors Engineering
Final Exam
100
Engineering
05/09/2010

Term
 Measurement and Assessment of manual lifting
Definition
 BiomechanicalPhysiologicalPsychophysical
Term
 Factors affecting lifting ability
Definition
 Task: -weight, height of lift-frequency of lift-load distance from body-load distance from floor(bending)-load position relative to sagittal plane(twisting)-C.M. of load-load dimension and characteristics-handles-lifting techniquePersonal:-strength-body size-experience and knowledge of task-attitudeEnvironmental:-floor conditions(traction, plane)-vibration-illumination-heat and coldManagement:-frequency and length of rest breaks-variability of tasks(job rotation or enrichment)-overtimePsychosocial:-attitude to work-interaction with coworkers
Term
 Most efficient lift range and weight
Definition
 40-60 inches off floor and about 40 lbs
Term
 Scientific guides for protection from injuries
Definition
 -The NIOSH lifting equation-The Job Severity Index(Texas Tech)
Term
 Biomechanical Measurement and Assessment(limits)
Definition
 This criterion is for infrequent, heavy lifts-Compressive forces over 6400N at the L5/S1 disc is considered dangerous-3400-6400N is considered a range which injury is likely to occur-Below 3400N is considered safe
Term
 Psychophysical measurement and assessment
Definition
 Determines the max acceptable lifting weight(MAL)MAL-the max weight a worker is willing to lift and is capable of lifting for a shift, at work
Term
 Metabolic lifting limits
Definition
 9.5 kcal/min for 8hr jobs-50% of the person's PWC(VO2 Max) for 1hr-40% for 1-2hrs-33% for 2-8hrs
Term
 NIOSH equation
Definition
 Computes a RWL based on a constant factor LC adjusted for 6 work variable(multipliers). Biomechanical, metabolic, and psychological criteria in the form of one equation.HM-distance of the person from loadVM-Height of the object at the start of the liftDM-Vertical range of the liftAM-Amount the upper body is twistedFM-Frequency-duration-range of lift comboCM-How good the handle coupling is
Term
 Lifting Index(LI)
Definition
 LI=L/RWLif LI > 3 the work is at great risk to injury
Term
 Information
Definition
 reduction of uncertainty
Term
 bit
Definition
 the amount of information uncertainty required to decide between two equally likely alternatives.Hi=log(base2)(1/pi)=ln(1/pi)/ln(2)For 2 equally likely event H=1For 4 H=2For 16 H=4
Term
 H ave
Definition
 SUM(pi*log2(1/pi)
Term
 % redundancy
Definition
 [1-(Have/Hmax)]*100
Term
 Hmax
Definition
 bits if probabilities were equal
Term
 Hick-Hyman Law
Definition
 The choice reaction time is a linear function of (log(base2)N the number of bits of information in the stimulus
Term
 Display
Definition
 any indirect method(stimuli) of presenting information
Term
 Types of Displays
Definition
 any indirect method(stimuli) of presenting information -speeding zone on a speedometer, closed/open signWarnings and SignalsRepresentational information-photos, mpas, graphsIdentification displays-color codes pipes, slippery road signAlphanumeric and symbolic -textbook material, brailleTime-phased-morse code, blinker lights
Term
 When are auditory better than visual displays? When message is....
Definition
 simpleshortnot to be referred to latertime sequencedof emergency typevision is overburdenedbrightness and glare present visual -problemsmovement of person is necessary
Term
 Relative Judgement
Definition
 Compare stimuli and judge positions along a dimenstion-compare two sounds to determine the louder one
Term
 Absolute judgement
Definition
 Identifying without actually comparing-identifying an aircraft as a military one-people can make about 7+-2 identifications on absolute basis-can make less discriminations than relative basis-Can be orthogonal or redundant and will increase the number of stimuli
Term
 Orthogonal Coding/Dimension
Definition
 Value of one dimension independent of another-red square is different from green square or red circle
Term
 Redundant Coding/Dimension
Definition
 Knowing the value of one dimension helps predict the value of the other dimension-all square are green, all triangles are red, all circles are blue
Term
 How many pairs of sounds differing in tone pitches can people discriminate(relative basis)?
Definition
 1800
Term
 How many sounds can be identified(absolute basis)?
Definition
 5
Term
 When do we display information?
Definition
 When sensing is inadequate due to stimulus being-below threshold of detectability-too large-embedded in excessive noise-removed or obstructed-sensed with low precision-to be stored-convertible(same or diff modality)-inherently of display type
Term
 What happens when orthogonal/redundant dimensions are combined?
Definition
 Orthogonal-increase the number of stimuli that can be identified, but produces less than product of the seperate numbers. So redundant combos of 4 colors and 3 shapes yield more than 4 but less than 12 size/ color combos.Redundant-Increase the number of indentifiable signals to more than the number for a single dimension but yields less combos than orthogonal dimensions.
Term
 5 Main Display Modalities(Senses)
Definition
 VisualAuditoryTactual/Tactile/TouchOlefactory/SmellTaste
Term
 Visual Acuity
Definition
 The ability of the eyes to differentiate between the detailed features of what we seeVA=3438H/DAcuity=1/VA
Term
 Convergence
Definition
 The ability of the 2 eyes to position the object being viewed at corresponding positions so that the 2 images are fuseddefect=phorias-the inability to converge properly resulting in double vision
Term
 Color discrimination
Definition
 Cone cells in retina are responsible
Term
 Accommodation
Definition
 The adjustment of the lens of the eyes to focus images sharply on the retina
Term
 Myopia
Definition
 Difficulty in seeing sharply at far distances but not close up-short-sightedness
Term
 Hypermetropia
Definition
 Difficulty in seeing close up but not at far distances-hyperopia or far-sightedness
Term
 Minimum Seperate Acuity
Definition
 The smallest feature, or smallest space between parts of a target, that the eyes can detect
Term
 Visual Angle(VA)
Definition
 Measures the detail that can be ween as the angle(in minutes of arc) the target makes with the eye.VA=3438H/D H=height of object D=distance from eyeAcuity=1/VA
Term
 Color Defect
Definition
 Inability of some people to discriminate between some colors-red and green are often confused-blue and yellow are often confused-inherited or acquired-8% males, 0.5% females
Term
Definition
 Ability to adapt to different levels of light intensity so that eye retina is not overexposed or underexposedLight to dark=30min or moreDark to light=few sec to 2min
Term
 Luminance contrast
Definition
 The difference in luminance of the features of the object being displayed object vs backgroundcontrast=[(B1-B2)/B1]*100B2 is the brighter of the twoFor low contrast enlarge target
Term
 Amount of illumination
Definition
 -depends on task -should not vary more than about 5:1 in adjacent areas -very high levels may 'wash' away different gradients public areas - 20-50 lux offices - 400-500 lux surgical procedures - 10,000-20,000 lux
Term
 Time
Definition
 discriminability increases with viewing time
Term
 Luminance ratio
Definition
 3:1 for task and surrounding area in office
Term
 Glare
Definition
 direct and reflected(specular)-discomfort glare-disability glare-blinding glare
Term
 Movement
Definition
 -decreases the threshold of visual acuity-The ability to make visual discriminations is called dynamic visual acuity(deg/sec)-acuity decreases rapidly beyond 60 deg/sex
Term
 Reflectance
Definition
 the ration of the amount of light reflected(luminance) by a surface to the amount striking the surface(illuminance)refl=luminance(cd/sq-m)/illuminance(lux)
Term
 Personal Factors
Definition
 with age presbyopia occurs-lens becomes discolored and less flexible, so light intensity must increase and more time must be allowed for refocusing
Term
 Perception
Definition
 meaning vs seeingA desing should help people perceive what they sense.Training may be needed
Term
 HF criteria for good visual displays
Definition
Term
 Visibility
Definition
 Targets detectable from surroundings
Term
 Legibility
Definition
 Targets identifiable from others
Term
Definition
 Recognition and meaningfulness
Term
 Standardization
Definition
 when codes are to be used by different people in different ways
Term
 Typography
Definition
 refers to various features of the characters and their arrangements-viewing conditions, information importance, distance, and visual acuitystroke width-ratio of stroke thickness to character height-white on black(1:8 to 1:10)-black on white(1:6 to 1:8)-illumination levelwidth to height ration-capital letters(1:1)-numerals(3:5)FontsEffect legibility, visibility, readability
Term
 Important principles of symbolic design
Definition
 figure/ground-should be clear and stablefigure boundaries-solids better than outlinesClosure-enhances perceptual processes relative to discontinuous outlinesSimplicityUnity-Symbols should be unified-a solid figure should be within an outline, not outside it
Term
 4 Main uses of Dynamic Displays
Definition
 QuantitativeQualitativeStatusRepresentational information
Term
 Usefulness of aircraft, geometric, military, and color coding
Definition
 1-colors2-military symbols3-geometric shapes4-aircraft shapes
Term
 3 types of Quantitative displays
Definition
 Fixed scale with moving pointer-best when values are suject to frequent or continual change that would preclude the use of a digital display, when it is important to observe the direction or rate of change of the values presented.-most often preffered over moving scale with fixed pointerMoving scale with fixed pointer-When there is a large range of value with small displayDigital Display-best when precise numeric value is required, the values presented remain visible long enough to be read-Semi/Circular is favored over vertical or horizontal
Term
 What do Qualitative Displays Depict
Definition
 Trends, Rates of change, approximate values
Term
 Quantitative basis for qualitative data
Definition
 -Determine status of condition of variable-Maintain desired range-observe trends
Term
 Important features of quantitative scales
Definition
 numerical progression-1s, 5s, 10s-not 3s, 8sLength of scale unit-smallest unit to read/measure-smallest is 1.3-1.8mmScale markers-at every scale unit to be read-interpolation(rounding)Design of pointer-tip angle of 20deg-have tip meet smallest scale markers-color-pointer close to surface(parrallax)Scale size & viewing distance-viewing distance = 28in(71cm)-maintain same viewing angle at further distances
Term
 Factors influencing detectability of signal and warning lights
Definition
 Size, Luminance, Exposure timeColor-consider background color and ambient illumination-not important for bright signal-for weak use red, green, yellow, white in that orderFlash rate - below flicker-fusion frequency (30/s)-use 3-10 per sec with 0.05s durationBackground lights
Term
 Recommendations for signal and warning lights
Definition
 When-to warn of dangerous conditionsHow many-one ideallySteady state of flashing-flashing for extreme emergency since its distractingFlash rate- 3-10/sec(4 best) at equal intervals of light and darkWarning light intensity-light should be at least twice as bright as immediate surroundingsLocations-within 30deg of the normal line of sightcolor-red
Term
 4 different types of decisions according to Signal Detection Theory
Definition
 HitMissFalse AlarmCorrect Rejection
Term
 SDT examples
Definition
 Conservative operator-miss rate is minimized and hit rate is maximized. False alarms are increasedSurgeon who doesnt want to miss a case for surgery-will end up performing more surgeries unnecessarily(increase false alarms)
Term
 Human Error
Definition
 An inappropriate or undesirable human decision or behavior that reduces or has potential for reducing effectiveness on safety of system performance
Term
 IE Error Classification
Definition
 Assumes that errors are from dicrete action-error of ommision-error of commission-sequence error-timing error-extraneous act
Term
 SOR error classification
Definition
 error viewed as a break in the stimulus-organism-response chain(as input, mediation, or output error)-failure to perceive stimulus-inability to discriminate among various stimuli-misinterpret of meaning of stimulus-not knowing correct response to stimulus-physical inability to make response-responding out of sequence
Term
 Memory
Definition
 The process of storing incoming information in brain storage capacity of human memory - 10^8 to 10^15 bits-Sensory Storage-Working/Short term-Long term
Term
 Sensory storage
Definition
 Prolongs stimulus for a short period after cessation of presentationIconic Storage-Visual(1 sec)Echoic Storage-Auditory(few sec)
Term
 Working memory
Definition
 Phonetic-the visually presented word DOG is phonetically coded as the sound generated from reading the wordSemantic-abstract representations of the meaning of a stimulus rather than the sight or sound generated by the stimulus
Term
 We give more weight to early information
Definition
Term
 We do not extract enough information as we should
Definition
Term
 Odds are not assessed as extremes, as they should be
Definition
Term
 We increase our confidence, but not necessarily our accuracy, with more information
Definition
Term
Definition
Term
 We treat all information equally reliably
Definition
Term
 We cannot entertain more than 3 or hypotheses at a time
Definition
Term
 We consider only a few attributes at a time
Definition
Term
 We choose information supporting a chosen course of action
Definition
Term
 A potential loss is viewed with greater influence than a gain of similar amount
Definition
Term
 -We believe that mildly positive outcomes are more likely than mildly negative ones-Highly positive outcomes are more likely than mildly positive ones-Highly negative ones are less likely than mildly negative ones
Definition
Term
 Computer aided decision making can help eliminate biases
Definition
Term
 Selective Attention
Definition
 Monitor several sources of information but performance decreases-increases load stress which is more dominant than speed stressGuidelines-Use as few channels as possible-Let subject which channel is more important so can direct more attention -Reduce overall effect of stress-Provide preview of information-Train subject to scan optimally-Place visual channel close together-Do not mask auditory channels-Rate of storage should be controlled
Term
 Focused Attention
Definition
 Attend to one source of information and exclude all others-Influenced by proximity in physical space of resources and maskingGuidelines-Have distinctions in competing channels-Separate competing channels-Reduce number of competing channels-Make channels more conspicuous than competing channels
Term
 Divided Attention
Definition
 Pay attention to 2 or more tasks, performed simultaneously(multi-tasking)-performance decreases because capacity to process info is overwhelmedGuidelines-Minimize number of potential tasks-For time sharing let the subject know priorities of tasks-Lower the difficulty level of tasks-Make tasks as dissimilar as possible-Use physical as well as mental resources, Manual time shared tasks interfere less with sensory or mental tasks
Term
 Direct/Indirect Sensing
Definition
 Direct-direct observation of an airplaneIndirect-through a mechanism or deviceRadar or telescope
Term
 Coded/Reproduced Stimuli
Definition
 Coded-Visual or auditory displaysReproduced-tv, radio, photos, microscopes, binoculars, hearing aids
Term
 Static/Dynamic Displays
Definition
 Static-printed, written, traffic signs, charts, graphs, labelsDynamic-Information continually changes
Term
 Cones
Definition
 Daytime vision & color discrimination
Term
 just noticeable difference(JND)/difference threshold
Definition
 the smallest detectable difference that can be discriminated on a relative basis
Term
 Reliability
Definition
 Series-failure occurs when any component fails. component failures are independentR=R1*R2*R3*R4Parallel-failure occurs when all components failR=1-[(1-R1)(1-R2)(1-R3)(1-R4)]Hybrid-Combo of series/parrallelR=1-(1-R1*R2*R3)(1-R1*R2)R=[1-(1-R1)(1-R2)(1-R3)][1-(1-R1)(1-R2)]
Term
 4 Principles of Work Area Design
Definition
 ImportanceFrequency of UseSequence of UseFunction
Term
 Importance Principle
Definition
 Put most important work items in most visible and accessible areas
Term
 Sequence of Use Principle
Definition
 The sequential arrangement of equipment should correspond to the sequence of use
Term
 Functional Principle
Definition
 Equipment that are functionally related should be placed near each other
Term
 Frequency of use principle
Definition
 equipment that are most frequently used should placed in the most accessible areas
Term
 Work Postures-Sitting(when and why)
Definition
 -to prevent muscular fatigue-to maintain body stability and arm positions-when worker must us foot controls-when fine assembly, writing and precision hand work are required-when the hands will not work at more than 6in above work surface-when work period is long
Term
 Work Posture-Standing(when and why)
Definition
 -work periods are not lengthy and muscular fatigue is not a problem-mobility of the body is required-great manual forces are required and objects above 10lb are handled frequently-high, low or extended reaching is frequent-adequate leg room is not available
Term
 Line of Sight
Definition
 neck is about 10deg in flexion and the eyes are rotated downward moderately
Term
 Different Work Postures
Definition
 SitStandSit-StandKneelLying DownVariable
Term
 Major Principles of Workplace Design
Definition
 -keep number of items touched by hand to minimum-arrange items so that operator can adjust body posture easily-identify primary and secondary movement envelopes on the work table---primary is 16in(40cm) for 5% woman, secondary is 24in(60cm)-consider preferences in hand movements and handedness-distinguish between primary and secondary items-divide tasks into subtasks, each forming a logical unit-divide work table into several areas to conform subtasks-place items such as tools and bins in a convenient location so they can be used in a logical sequence
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