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Human Computer Interaction
Raheela Firdos
Introduction
• New technologies provide extraordinaryalmost supernatural powers to those people
who master them.
• Great excitement spreads as designers provide
remarkable functions in carefully crafted
interactive devices and interfaces.
Conti……
• Early computers were usable only by people who
devoted effort to mastering the technology.
• The interdisciplinary design science of human
computer interaction began by combining the data
gathering methods and intellectual framework of
experimental psychology with the powerful and
widely used tools developed from computer science
Conti……
• contributions accrued from educational and
industrial psychologists, instructional and
graphic designers, technical writers, experts in
human factors or ergonomics, information
architects, adventuresome, anthropologists
and sociologists
Importance
• In the aftermath of the September 11, 2001
terrorist attacks, some members of the U.s.
Congress blamed the inadequacies of user
interfaces for the failure to detect the
terrorists.
Conti……
• At an individual level, user interfaces change
many people's lives effective user interfaces
for professionals mean that doctors can make
more accurate diagnoses and pilots can fly
airplanes more safely; at the same time,
children can learn more effectively and
graphic artists can explore creative
possibilities more fluidly.
Conti……
• A significant number of people take advantage
of the World Wide Web's remarkable
educational and cultural heritage resources, egovernment services, and health-support
communities.
• Making these diverse applications successful
requires contributions from researchers and
practitioners in many fields
Conti……
• The plasticity of their designs must ensure
smooth conversion across display-size
variations, delivery by way of web browsers or
the telephone, translation into multiple
languages and compatibility with accessibilitysupport devices for disabled users.
Conti……
• The inspirational pronouncements from
technology prophets can be thrilling, but rapid
progress is more likely to come from those
who do the hard work of tuning designs to
genuine human needs.
Usability Requirements
• Designers propose multiple design
alternatives for consideration, and the leading
contenders are subjected to further
development and testing.
• User-interface building tools enable rapid
implementation and easy revision.
Conti……
• Evaluation of designs refines the
understanding of appropriateness for each
choice.
• Successful designers go beyond the vague
notion of "user friendliness," probing deeper
than simply making a checklist of subjective
guidelines.
Conti……
• Effective interfaces generate positive feelings
of success, competence, mastery and clarity in
the user community.
Human Engineering Design Criteria (1999)
• The U.s. Military Standard for Human
Engineering Design Criteria (1999) states these
purposes
Achieve required performance by operator,
control, and maintenance personnel.
Minimize skill and personnel requirements
and training time.
Conti……
Achieve required reliability of personnelequipment/software combinations.
Foster design standardization within and
among systems.
• These functional purposes are good starting
points, but effective interfaces might also
enhance the quality of life for users or
improve their communities.
Goals
• The first goal in requirements analysis is to
ascertain the users/ needs-that is, what tasks
and subtasks must be carried out. The
frequent tasks are easy to determine, but the
occasional tasks, the exceptional tasks for
emergency conditions, and the repair tasks to
cope with errors in use of the interface are
more difficult to discover.
Conti……
• A vital second goal is to ensure proper
reliability actions must function as specified,
displayed data must reflect the database
contents, and updates must be applied
correctly.
• Users/ trust of systems is fragile; one
experience with misleading data or
unexpected results will undermine for a long
time a person/s willingness to use a system.
Conti……
• The third set of goals for designers is to
consider the context of use and promote
appropriate standardization, integration,
consistency, and portability.
• As the number of users and software packages
increases, the pressures for and benefits of
standardization grow.
Conti……
• Incompatible storage formats and hardware
and software versions cause frustration,
inefficiency, and delay.
Conti……
• Standardization refers to common userinterface features across multiple applications.
 Apple Computers 0992,2002) successfully developed
an early standard that was widely applied by
thousands of developers, enabling users to learn
multiple applications quickly.
 When the Microsoft Windows 0999,2001) interface
became standardized
Conti……
• Integration across application packages and
software tools was one of the key design
principles of Unix.
• Consistency primarily refers to common action
sequences, terms, units, layouts, colors,
typography, and so on within an application
program. Consistency is a strong determinant
of success of interfaces.
Conti……
• Portability refers to the potential to convert
data and to share user interfaces across
multiple software and hardware
environments.
• The fourth goal for interface designers is to
complete projects on schedule and within
budget.
Conti……
• Proper attention to usability principles and
rigorous testing often lead to reduced cost
and rapid development.
Usability Measures
• Multiple design alternatives must be
evaluated for specific user communities and
for specific benchmark tasks.
• A clever design for one community of users
may be inappropriate for another community.
• Time to learn.
How long does it take for typical members of
the user community to learn how to use the
actions relevant to a set of tasks?
Speed of performance.
How long does it take to carry out the
benchmark tasks?
• Rate of errors by users
How many and what kinds of errors do people
make in carrying out the benchmark tasks?
Although time to make and correct errors might
be incorporated into the speed of performance,
error handling is such a critical component of
interface usage that it deserves extensive study.
• Retention over time.
How well do users maintain their knowledge
after an hour, a day, or a week?
Retention may be linked closely to time to learn,
and frequency of use plays an important role.
• Subjective satisfaction
How much did users like using various aspects of
the interface?
The answer can be ascertained by interview or
by written surveys that include satisfaction
scales and space for free-form comments.