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