ISEN 330 Week3

Constraints

strict requirements for system design (the design must…)

Objectives

goals for improvement efforts (the design should strive to…)

Stakeholders

those who have some "stake" or interest in the functioning of the current system, or those who would be impacted in a newly-designed system

Functions

what the system is supposed to do, fulfilled by tasks

Tasks

activities that are performed so that system functions are fulfilled

Function analysis

description of basic system functions that help users achieve goals

Task analysis

individual tasks/activities to fulfill basic system functions

Persona

a hypothetical user developed through interviews and observations of real people who will use the system

Observation

watch a person in context as they perform a task

Contextual inquiry

observe in context, assume an "apprentice" role and have the observed person "teach" you the task, explaining why they do certain things

Think-aloud verbal protocols

User thinks aloud as he/she performs task

Unstructured interviews

allows for "exploratory" questioning but can be very inefficient

Structured interviews

specific, pointed questions prepared before interview

Focus group

interview discussions with 6-10 users, led by a facilitator

Incident

noticeable problem occurs, but something is done to save the system before an accident

Construct validity

Adequacy of the operational definitions for both the independent and dependent variables

External validity

Degree to which the research findings generalize beyond the specific context of the conducted experiment

Internal validity

Degree to which an experiment is methodologically sound and confound-free

Statistical conclusion validity

The extent to which the researcher uses statistics properly and draws appropriate conclusions from the analysis

Light

Electromagnetic radiation

Cornea

layer of skin that protects the eye and refracts (bends) light

Pupil

opening that can dilate/constrict to let in more/less light

Lens

transparent material that changes shape to focus light

Retina

array of receptor cells in the back of the eye

Accommodation

adjustment of the lens power by control of the ciliary muscles

Fovea

center of visual focus, highest acuity, almost all cone receptors

Dark-adapted sensitivity

ability to see with very low levels of light

Purkinje shift

As we switch from cone to rod vision (day to night), shorter wavelengths appear brighter (green objects appear brighter, red objects appear darker).

"blue" cones

sensitive to short wavelengths (430 nm)

"green" cones

medium wavelengths (530 nm)

"red" cones

long wavelengths (560 nm)

Hit (H)

There is a signal and the operator detects it.

Correct rejection (CR)

There is no signal and the operator confirms this.

Miss (M)

There is a signal, yet the operator misses it.

False alarm (FA)

There is no signal in the environment, but the operator indicates signal.

Sensitivity of observer

Ability of operator to discriminate signal from noise

Refraction

bending light to focus on retina

Refractive power

The degree to which a lens converges or diverges light

Refractive error

when the combined efforts of cornea and lens cannot bring an image into focus

Myopia

"nearsightedness"

Hyperopia

"farsightedness"

Presbyopia

"old-sightedness"

Visual acuity

Ability to detect and discriminate fine details of objects at distance.

Visual angle

Visual angle refers to the angle formed by lines extending from the edges of an object (or image) to the eye's lens. This angle determines how large an object appears to the viewer. The larger the visual angle, the larger the object appear

Contrast

The difference in luminance between light and dark areas in a visual display, or between foreground/background

Readability

is the ease in which the whole text can be read and understood.

Legibility

is a measure of how easily individual letters or characters can be distinguished from each other.

Occlusion

If object A partially hides object B from view, A is closer than B

Relative height

Near to the horizon: further away Far from the horizon: closer

Relative size

Comparing two objects w/ belief they are the same size

Perspective convergence

Parallel lines become closer together with greater distance

Atmospheric perspective

objects that are farther away look less sharp and bluer than close objects

Texture gradient

elements that are equally spaced in a scene become more dense with increasing distance

Binocular disparity/stereopsis

Difference in locations of objects in the images seen via each eye, due to the two different viewpoints

Luminous flux

total electromagnetic energy emitted by a light source in all directions

Luminous intensity ( I )

electromagnetic energy emitted in a particular direction

Subtended solid angle

steradian

Illuminance (E)

energy from the light source that strikes the surface of an object to be seen

Luminance ( L )

amount of light energy reflected off the object's surface

Angle of incidence

Angle between a line normal to the illuminated surface and the line from source to that surface

Normal line

perpendicular to surface in all meridians

Direct glare

too much light in the eyes from a source (lamp, sunlight, window, etc)

Reflected glare

too much light over an extended area illuminated by some source

Disability glare

lessens the ability to see detail without necessarily causing visual discomfort

Discomfort glare

causes visual discomfort without necessarily lessening the ability to see detail

Direct radiant lighting

90% or more of light is directed toward workspace

Indirect lighting

90% or more light is directed upward towards ceiling

Phototropism

tendency to move our eyes toward bright lights (windows!)

Sound

propagated vibrations through a medium (e.g., air, water)

Amplitude/intensity

magnitude difference between max and min air pressure in wave. Defines the perception of "loudness"

Frequency

defines perception of "pitch"

P (Sound power)

sonic energy per unit time (Watts)

Bels

Log-transformed ratios

decibel (dB)

1/10th Bel

dB SPL

Sound Pressure Level

dB SIL

Sound Intensity Level

dB SWL

Sound Power Level

Loudness

describes psychological experience, in units of sones

1 sone

loudness of 1000 Hz tone at 40 dB