Human Factors Exam 1
Gain
(change of the cursor)/(change of control position) High gain = small change in control displacement yields a large or fast entity movement. Ideal is between 1 and 3
Steps in conducting experiment
1) Define your problem and hypothesis 2) Specify your experimental plan 3) Conduct the Study 4) Analyze the data 5) Draw your conclusions
Rank the 6 Control Codings by Importance
1) Location 2)Color 3)Size 4)Shape 5) Labelling 6) Mode of operation
Signal Detection Theory (name outcomes)
1) Present and Detected = Hit 2) Not present and detected = False alarm 3)Present and not detected = miss 4) Not present and not detected = correct rejection
Two types of eye movement
1) Pursuit - smooth movements 2) Saccadic - rapid movements
Six stages of HFE in Product design life cycle
1)Front end analysis 2)Iterative design and test 3)System production 4)Implementation and evaluation 5)System operation and maintenance 6)System disposal.
Organization of Controls (How you should set things up)
1)Organize by function and sequence of use 2)Guard against accidental activation 3)Standardize within operations and industry 4)Keep most frequently used controls in the primary envelope
The ear is most sensitive to which ranges of frequencies?
1,000 - 4,000 hertz
Visible light range
380 nm to 740 nm
Task Analysis
A way to systematically describe human interactions with a system or product
Visual Acuity
Ability to detect small details and discriminate small objects
Contrast sensitivity
Ability to perceive small differences in luminance
Usability Heuristics -Flexibility and Efficiency
Accelerators help speed up interactions for expert users such that your product is desirable by experienced and inexperienced users. Ex) Bookmarks
Middle Ear (purpose and anatomy)
Accentuates signals and transfers energy to the Cochlea. Chain of three small bones. Malleus, Incus, and Stapes
The process of the muscles contracting and relaxing to squeeze or flatten your lens is known as what?
Accommodation
Perceptual Principles
Add on Notecard
Usability Heuristics -Recognition vs. Recall
Allow users to see where they are instead of making them remember the path they took to get there
Controlling Noise
At the source: Enclose the source Change the design or equipment Along the Path: Increase distance and use barriers At the host: PPE and job rotations
Hindsight Bias
Believing after the fact that the outcome was foreseeable or predictable
Near sighted
Can't see things well unless they are close
Far sighted
Can't see things well unless they are further away
Fovea
Central part of the retina, contains only cones. Needed to tell the color of something
Motion Parallax
Change in perceived location or movement of an object caused by a change in observer position relative to the object in question.
The part of your eye that contracts and relaxes to squeeze or flatten your lens is known as what?
Ciliary Muscles
External Ear (purpose and anatomy)
Collects sound waves and forces them into the ear drum. Pinna - External Ear issue Auricle - external ear canal and eardrum
Design Implications - Sight
Color coding is useless in dark environments. Have a 30-40 degree visual cone. Viewing angle is 15 degrees below the horizontal. Increase contrast and illumination. Consider type of movement
A variable that can cause a false association in a study (such as a rise in both murders and ice cream sales at the same time, which may lead one to believe they are linked) is known as what?
Confounding Variable
Relating to signal detection theory, shifting the beta (response criterion or response bias) value to the right along the graph means that an inspector is:
Conservative
Control Design Principle 1
Control must appropriate for the task environment and the size of the control console
Response Selection - Feedback
Controls must provide feedback to support awareness of input
Inner Ear (purpose and anatomy)
Converts mechanical energy to neural impulses → brain. Cochlea - has hair receptors Semi-circular canals for balance
The analysis that assigns monetary value to various benefits that can be gained from human factors analysis is known as what?
Cost benefit Analysis
Iterative testing and design
Creating prototypes, evaluating them, and redesigning. This may continue for many iterations.
Control Design Principle 2
Design controls consistent with learned population stereotypes
Functional Allocation
Designers should identify an appropriate function for the human and the product. Determine whether each function is best performed by the system (automatic), the person (manual), or some combination.
Usability Heuristics -Minimalist Design
Dialogues should not have irrelevant information. Every extra unit of information competes with relevant information.
Contrast
Difference of luminance between objects. Not affect by illumination
Control Coding - Color
Different Colors can signify different control functions. Best to use redundancies
Learned intuition
Difficult to remember not knowing something
Displays and Controls definitions
Display - presents feedback, conveys to human senses Controls - Allow operator's inputs, tasks to be accomplished
Control Coding - Size
Doesn't depend on visual cues. Must take just noticeable threshold into account.
User Centered design
Early focus on user and tasks, iterative design
Work System Model
Elements include anything involved in any basic work system. All elements in a system interact with each other. Misfits can lead to productivity, efficiency, safety, and quality issues.
Redistribution of error
Error does not truly go away, but instead occurs in a different part of the system
Factorial Design
Evaluating more than one independent variable or factor in a single experiment
True or False: common sense is REAL and we love it and rely on it in human factors
False
True or False: the cilia in your inner ear can be regrown/regenerated
False
What is Human Factors?
Fit between people and products, systems, environments, procedures, and facilities. How work design affects people
Systems Center Approach
Focus on the conditions in which the problem occurs. Build defenses to avert opportunity for errors and mitigate their effects
Person Centered approach
Focused on individuals. Blame human error including inattention, carelessness, or forgetfulness
Permanent threshold shift
Gradual and can go unnoticed over time and Cannot be fixed
Multiple Group Design
Have an independent variable but want to test multiple levels of the variable
Usability Heuristics -Help and Documentation
Help and documents should be easy to search and access
Shifting response Bias
High B = shifted to right (conservative) Low B = shifted to left (risky) center B (average)
Fitt's Law says that movement time is related to both amplitude of movement and width of the target; smaller targets result in
Higher index of difficulty
Relating to signal detection theory, what is the condition called when an operator says a signal is present and a signal IS present?
Hit
What increases in SDT when you tell operators to pay more attention and to not miss defects?
Hit rate and False alarm rate increase.
Control Coding - Mode of Operation
How the control works can tell you what it's used for, activated by a unique movement.
Visibility
How well an object is seen by the human eye. Affected by illumination and contrast.
Color
Humans can recognize 9 distinct colors with 24 total. Used in Quantitive and Qualitative displays. Color coding can be very useful in search tasks
4 HFE Processes
Identify, Analyze, Design, and evaluate
Response Selection - Speed Accuracy Trade Off
If you design a control according to the principles mentioned, there is no inherent speed-accuracy tradeoff. If you must perform very fast, accuracy will suffer If you must be very accurate (life or death consequences) then you must act slower.
Glare
Indirect - from reflected light Direct - from source
Confounding variables
Influences both dependent and independent variables
Illuminance
Intensity of incident light on a surface. "Falls" onto surface
Luminance
Intensity of light emitted or reflected from a source in a given direction. Luminance Flux = intensity of source
Common Sense...
Is a myth and design process must take into account all user characteristics
Eye anatomy
Light passes through the cornea -> Light passes through the pupil -> Ciliary muscles focus imagine on the retina -> Light stimulates retina -> Photoreceptors transmit data to brain
Adaptation
Light to dark takes 30-60 min Dark to light takes 30-60 seconds
Having controls located as close as possible to the entity being controlled or the related display is known as what?
Location Compatibility
Response Selection - Compatibility
Location compatibility = Having controls located as close as possible to the entity being controlled or the display of that entity. Movement compatibility = Having the direction of movement of the control correspond to the movement of the system and displayed feedback.
Control Coding - Location
Locations can be learned quickly and stereotypes develop quickly. Need to be conscious of accidental activation
Time motion study (4 cases)
Low value and lots of time = Do less Low value and little time = Ignore High value and lots of time = do better High value and little time = Do more
Control Device - Tracking
Making a system output correspond in time and space to a time-varying command target input. Frequency of connections need to be made.
3 Types of noise problem
Masking, Startle response, and Temporary Threshold shift (Hearing loss)
Temporary Threshold shift
May damage your hair cells (cilia), but not totally destroy them and they will likely recover.
Multiple Dependent Variables
Measure how casual variables affect several dependent variables at once
Relating to the anatomy of your ear, the ossicles, used to translate mechanical sound energy into your cochlea, is located in what part of the ear?
Middle
Fitt's Law (difficulty index)
Movement time and difficulty index increase with greater amplitude as well as smaller targets. If DI and movement are decreased, precision will be decreased.
A study that measures how casual variables affect several dependent variables at once is known as what?
Multiple dependent variable design.
Masking
Noise can prevent people from hearing vital communications, information from signals or alarm sounds. Can combat it by decreasing the noise or by increasing the signal (can also add visual alerts)
Noise and Performance Effects
Noise effects cognitive work. Noise appears to have little impact on motor performance or sensory functions
Startle Response
Noise is too loud it startles the person. Bad for skills that require fine motor skills
Ways to collect task data
Observation, Task performance with questioning, Interviews, Think aloud protocol: Users verbalize everything they do to accomplish the task.
Relating to the anatomy of your ear, the auricle, used to collect sound energy and direct it into the ear is located in what part of the ear?
Outer
Proprioception
Perception or awareness of the position and movement of the body
The approach that blames operators for errors citing inattention, carelessness or forgetfulness is known as what?
Person Centered
What does human factors include
Physical, cognitive, and organizational/Macro aspects
Control Coding - Shape
Powerful control that doesn't require visual cues
Usability Heuristics -Error Recovery
Precisely indicate the problem and suggest solutions.
Auditory Alarms
Preferred to visual alarms because they are omnidirectional and it is harder to close your ears than eyes. Make sure alarm sounds like the condition it represents.
As light passes through the ________________ , it dilates or constricts to adjust to lighting levels
Pupil
Multiple Display Principles
Put displays of high importance and frequently used near the primary visual area
Cost Benefit Analysis
Puts a monetary value on efforts, can be hard to quantify some things
The phenomenon where an error does not truly go away, but instead occurs in a different part of the system is known as what?
Redistribution Error
Tritanope
Reduced sensitivity to blue light (very rare)
Deuteranope
Reduced sensitivity to green light (most common)
Protanope
Reduced sensitivity to red light
Objectives of Human Factors
Reducing errors, fatigue stress, and injuries while improving productivity, ease of use, safety, etc.
Reflectance
Reflective ability of a surface on a scale of 0-1. Paper is an .85
Response Selection - Expectancy
Response time and accuracy of control selection improves with compatibility of control design and function with expectations.
Tactile
Sensation is through the skin
Haptic
Sensation through the skin and kinesthetic senses
Cones
Sensitive to color but don't work well in the dark
Control Dimensions - small vs large
Small - Harder to manipulate but aid in accuracy. Large - useful when a task needs to be completed quickly
Sound
Sound is heard because of a change in pressure. Amplitude determines intensity/loudness. Frequency determines pitch. Audible range: 20Hz - 20,000 Hz Most sensitive 1,000 Hz - 4,000 Hz
Noise
Sound that is unpleasant, distracting, unwarranted or in some other way undesirable.
Response Selection - Decision Complexity
Speed that an action can be selected is influenced by the number of alternative actions that could be selected. Smaller number of complex decisions is better than a large number of small decisions
Design Guidelines - Sound
Start with a user, task, and environmental analysis. Auditory signals should be at least 500 milliseconds in duration Signals should be 15 db above the threshold but no more than 25 db
Within Subject Designs
Subjects participate in all of the experimental conditions
The approach that focuses on the conditions in which the problems occur is known as what?
System Centered
Usability Testing
System should be easy to learn(learnability), system should be efficient, easy to remember, low error rate, and be pleasant to use
Usability Heuristics - Visibility
System should keep users informed about what is going on in a reasonable time
Usability Heuristics - Matching system and world
System should speak the users' language with words, phrases, and concepts. Familiarity to the user is more important than system-oriented terms.
Inferential Statistics
Tell you the likelihood that any differences between experimental groups are real and not just random fluctuations.
Response Bias
The bias that the operator responds signal or no signal. Affected by operator's expectancy
Touch Processing - Top Down vs Bottom up
Top-down Experiences → Knowledge/Long term memory → Perception Bottom-up Stimulus → Senses → Perception
What type of control device is most appropriate for continuous control devices where system output must correspond in time AND space to a time-varying target?
Tracking
True or False: human factors draws on a large knowledge base including anatomy, engineering, physics, and psychology among others.
True
True or False: the design process often includes multiple iterations of prototyping, evaluation, and redesign.
True
True or False: think aloud protocol is often used during task data collection.
True
Control Coding - Labelling
Undesirable but can be used with redundancy. Be aware of language barriers.
Usability Heuristics - Consistency and Standards
Use wording consistently, especially between button labels and link names. Users should not have to wonder if different words, situations, or actions mean the same thing.
Control Device - Positioning
Used to position (Indirect/Direct) something in space. i.e) mouse. Associated with movement of hand or foot to control and movement of the control. Feedback can affect performance if it takes too long.
Usability Heuristics - User control and feedback
Users often choose system functions by mistake and will need a get out of jail free card.
Ethics
When using people has participants in research, there are often very specific guidelines.
Usability Heuristics - Error Prevention
While error messages are good to let people know system status, it is better to avoid problems from occurring at all.
User analysis Questions
Who are your users/ideal users? User goals?
Cutaneous Senses
constant sources of sensory input through touch. Touch, Tactile, Temperature, Thermal, Electricity, Pain, and Nociception.
Ciliary Muscles
contract or squeeze the lens or relaxes to focus an image on the retina (accommodation). Squeeze for close up, relax for far away.
Cornea
covers the pupil
Pupil
dilates or constricts to adjust to lighting levels
Sensitivity
high sens = signal is far from noise and high probability of hits with few errors. Low sense example = alarm in a loud factory
Incident and Accidental analysis
incident: noticeable problem occurs during system operation, but an accident does not result from it. Accident systematically analyzed to determine root causes and where they arose: Human, Machine, or the interaction
Retina
lines the back of the eye and contains rods and cones
Model
mathematical/physical system, obeying specific rules and conditions, whose behavior is used to understand a real system to which it is analogous in certain respects
Contrast Sensitivity
minimum contrast that can be detected by the human eye. Raised lettering has poor contrast sensitivity. Need more contrast as you get older
Conductive loss
occurs when the eardrum fails to vibrate in response to sound because of some mechanical issue (outer/middle ear fails). Treatable
Sensorineural loss
occurs when the inner ear/nerve is injured by physical or other means. Cannot be fixed
Tapedius muscle
reflexively limits movement of the stapes to protect the ear from harmful noise
Descriptive statistics
summarize the dependent variable for the different treatment conditions, such as the mean or standard deviations
Optic Nerve
transmits image data to the brain
Usability Analysis
understand the user, their needs, and the demands of the work situation.
Environmental analysis
weather around product, temperature, wheelchair accessible?
Rods
work better in dim environments after a period of adaptation, not sensitive to color