The User Interface Design Process

The User Interface Design Process

• Organization design enables all the interface design should be

• Easily addressed, • clearly, and • Sequentially.

Obstacles in the Development Path• Nobody ever gets it right at the first time.• Development is chock-full of surprises.• Good design requires living in a sea of changes.• When decided to ignore change will never

eliminate the change.• Even if you have made the best system humanly

possible, people will still make mistakes when using it.

• Designers need good tools.

Pitfalls in the Development Path• Pitfalls in the design process exist because• A failure to address critical design issues, • An improper focus of attention, • Development team organization failures. • Common pitfalls are:• No early analysis and understanding of the user’s needs.• Little or no creation of design element prototypes.• No usability testing.• No common design team vision of user interface design

goals.• Poor communication between members of the development

team.

Usability• Bennett (1979) was the first to use the term

usability to describe the effectiveness of human performance.

• Shackel (1981) modified as “the capability to be used by humans easily and effectively”

Usability• Usability Assessment in the Design Process• Usability assessment should begin in the early

stages of the product development cycle and should be continue throughout the process.

• The assessment should include the user’s entire experience, and all the product’s important components.

Usability • Common Usability Problems• Mandel (1994) lists the 10 most common usability problems in graphical

systems as reported by IBM usability specialists. • They are:• 1. Ambiguous menus and icons.• 2. Languages that permit only single-direction movement through a system.• 3. Input and direct manipulation limits.• 4. Highlighting and selection limitations.• 5. Unclear step sequences.• 6. More steps to manage the interface than to perform tasks.• 7. Complex linkage between and within applications.• 8. Inadequate feedback and confirmation.• 9. Lack of system intelligence.• 10. Inadequate error messages, help, tutorials, and documentation.

Human Characteristics in Design• We are complex organisms with a variety of behaviors that

influence on interface and screen design. • The importance in design are• Perception,• Memory, • Visual acuity, • Foveal and Peripheral vision,• Sensory storage,• Information processing,• learning,• Skill, and • Individual differences.

Human Characteristics in Design• Perception• Perception is our awareness and understanding

of the objects • Through the physical sensation of our various

senses, including sight, sound, smell, and etc. • Perception is influenced, by experience. • we tend to match objects to things we already

know. • Other perceptual characteristics include the

following:

Human Characteristics in Design• Perception• Proximity. Our eyes and mind see objects as

belonging together if they are near each other in space.

• Similarity. Our eyes and mind see objects as belonging together if they share a common visual property, such as color, size, shape, brightness, or orientation.

Human Characteristics in Design• Perception• Matching patterns. We respond similarly to the

same shape in different sizes. • The letters of the alphabet, for example, possess

the same meaning, regardless of physical size.

Human Characteristics in Design• Perception• Succinctness. We see an object as having some

perfect or simple shape because perfection or simplicity is easier to remember.

Human Characteristics in Design• Perception

• Unity. Objects that form closed shapes are perceived as a group.

Human Characteristics in Design• Perception• Closure. Our perception is synthetic; it

establishes meaningful wholes. • If something does not quite close itself, such as

a circle, square, triangle, we see it as closed anyway.

• Continuity. Shortened lines may be automatically extended.

Human Characteristics in Design• Memory• Memory is not stable of human attributes. • Today, memory consisting of two components,

long-term and short-term (working) memory. • Short-term, or working, memory receives

information from either the senses or long-term memory, but usually cannot receive both at once.

Human Characteristics in Design• Memory• Within short-term memory a limited amount of

information processing takes place. • Information stored within it is vary to last from 10 to

30 seconds• Long-term memory contains the knowledge we possess. • Information received in short-term memory is

transferred to it and encoded it, a process we call learning.

• The learning process is improved, if the information being transferred from short-term to long-term

Human Characteristics in Design• Sensory Storage• People received the information which are stored in sensory memory• And transferred to short-term memory.• Sensory storage is the buffer to store information collected from our

senses• It is an unconscious process• Quick to detect changes, and constantly replaced by newly gathered• Sense, it acts like radar, constantly scanning the environment for things

and that are pass to the memory.• A common demonstration of SM is a child's ability to write letters and

make circles. • Design the interface so that all aspects and objects should define its

purpose. • Eliminating interface noise will ensure that important things will not be

missed.

Human Characteristics in Design• Visual Acuity• Visual acuity (VA) is clearness of vision• Dependent on the sharpness of the retinal focus within the eye• VA is the ability to identify black symbols on a white background

at a standardized distance as the size of the symbols is varied.• A visual acuity of 20/20 - means that a person can see detail

from 20 feet away the same as a person with normal eyesight would see from 20 feet.

• If a person has a visual acuity of 20/40, he is said to see detail from 20 feet away the same as a person with normal eyesight would see it from 40 feet away.

• A person with a visual field narrower than 20 degrees in diameter also meets the definition of legally blind.

Human Characteristics in Design• Visual Acuity Let the average viewing distance of a display screen is 19

inches , the size of the area on the screen of optimum visual acuity is 1.67 inches in diameter.

• Then assuming “average” character sizes and line spacing's, the number of characters on a screen falling within this visual acuity circle is 88, with 15 characters in the center line, and seven rows as follows

321312354321212345

6543211123456765432101234567

654321112345654321212345

3213123

Human Characteristics in Design• Visual Acuity• The eye is also never perfectly steady as it sees; • it trembles slightly. • This tremor, however, can sometimes create

problems. • Patterns of closely spaced lines or dots are seen to

shimmer. • This movement can be distracting and disturbing. • Patterns for fill-in areas of screens (bars, circles, and

so on.) must be carefully chosen to avoid this visual distraction.

Human Characteristics in Design• Foveal and Peripheral Vision • The foveal is responsible for sharp central vision (also

called foveal vision)• which is necessary in humans for activities such as

reading and driving…• The foveal is the central area of the retina• When we are "looking at" something, the image is

projected onto the foveal. • Foveal vision is used to focus directly on something;• peripheral vision senses anything in th surrounding that

we are looking at• Peripheral vision can aid a visual to search

Human Characteristics in Design• Foveal and Peripheral Vision • Peripheral vision decide to where the eye should go

next in the visual search of a screen. • Patterns, shapes, and alignments visible can guide

the eye in a systematic way through a screen.• What is sensed in the peripheral vision is passed on

to our information-processing system along with what is actively being viewed in the foveal.

• Care should be exercised in design to utilize peripheral vision in its positive nature, avoiding its negative aspects.

Human Characteristics in Design• Information Processing• The information that our senses collect should be

processed in some meaningful way. • There are two levels of information processing going

on within us. • Higher level & Lower level• The highest level, is identified with working memory. • It is slow, and sequential, and is used for reading and

understanding.• The lower level processes familiar information rapidly,

in parallel with the higher level.

Human Characteristics in Design• Information Processing• We look rather than see• Repetition and learning results in a shift of

control from the higher level to the lower level.• If a screen is jammed with information , it loses

its uniqueness and can only be identified through the more time-consuming

Human Characteristics in Design• Mental Models• From our experiences and culture, we develop mental models of things

and people we interact with. • A mental model is an internal representation of a person’s current

understanding of something. • Usually a person cannot describe this mental model. • Mental models are gradually developed in order to understand something,

explain things, make decisions, do something, or interact with another person.

• In a new computer system, people will bring their own expectations based upon mental models they have formed doing things in their daily life.

• While designing it is critical that a user’s mental models be to identified and understood.

• If the new system complies with already-established models, it will be much easier to learn and use.

Human Characteristics in Design• Movement Control• Once data has been received and an appropriate response

must be made; in many cases the response is a movement. • In computer systems, movements include such activities as

pressing keyboard keys, moving the screen pointer by pushing a mouse or clicking a mouse button.

• While designing screen:• Provide large objects for important functions.• Big buttons are better than small buttons. • Create toolbar icons• permitting much faster movements

Human Characteristics in Design• Learning• Learning, is the process of encoding in long-term memory

information that is contained in short-term memory. • Our ability to learn is important—it clearly different for

people and machines. • Given enough time people can improve their

performance in almost any task. • A design developed to minimize human learning time can

greatly accelerate human performance. • People prefer to stick with what they know, and they

prefer to jump in and get started.

Human Characteristics in Design• Skill• The goal of human performance is to perform

skillfully. • The skill is performance of actions or movements

in the correct time sequence • It can accomplished by mastering of the system

through such things as learning of shortcuts, increased speed, and easier access to information.

• System and screen design must permit development of increasingly skillful performance.

Human Characteristics in Design• Individual Differences• Individual differences are the variations from one person to

another • In reality, there is no average user.• Human characteristic all differ—in looks, feelings,

intellectual abilities, learning abilities and speed, and so on. • In a keyboard data entry task, for example, the best typists

will be twice as fast than an ordinary person and make fewer errors.

• The design must permit people with widely varying characteristics to satisfy different users.

• Design must provide for the needs of all potential users.

Human Characteristics in Design• Visual Acuity

Human Characteristics in Design