Cortesía de la clase de te

1. An introduction to usability
Dey Alexander
Usability Specialist
Monash University
dey.alexander@its.monash.edu.au
Version 1: July 2004

2. An introduction to usability
Table of contents
Aims of this workshop .............................................................. 3
What is usability? .................................................................... 4
The history of usability ............................................................. 7
Usability problems in our daily lives ............................................. 9
Why usability is important for the web ......................................... 17
Design challenges................................................................... 18
The role of the designer........................................................... 22
Human behaviour on the web .................................................... 27
User-centred design................................................................ 30
Exercises ............................................................................. 33
References........................................................................... 41
Resources ............................................................................ 42
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3. An introduction to usability
Aims of this workshop
This workshop aims to introduce participants to usability by:
• Introducing some common definitions of usability
• Identifying some of the experiential components of usability
• Providing examples of poor usability from everyday life
• Illustrating some basic human factors design principles that affect
usability
• Providing an overview of user-centred design
The workshop also provides an opportunity for participants to informally
evaluate the usability of several websites. Participants will play the role of
usability test observer and will be able to discuss their findings as a group.
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4. An introduction to usability
What is usability?
Consider some of the everyday experiences we have of things that are hard
to use:
• doors that we try to push open when we should have pulled them
• VCRs that we can't program
• telephone features, like “divert to voicemail” that we can never
remember how to use
• photocopiers or fax machines that we simply cannot fathom
• computer programs that take forever to understand
• websites where it takes ages to find what we are looking for.
Some things are a constant struggle to use and we find ourselves repeatedly
having to read the manual or ask our colleagues and friends to help us figure
out how to get them to work. Others work without problem, and as a result,
blend into the background as we go about our daily tasks.
The difference between difficult-to-use products or systems and those we
don't have to think about using is usability. In other words, usability is ease
of use.
Jakob Nielsen, a well known advocate of usability, says “usability is the
measure of the quality of the user experience when interacting with
something”.
A formal definition
In ISO 9241: Ergonomics requirements for office work with visual display
terminals, the International Organisation for Standardisation defines
usability as “a measure of the effectiveness, efficiency and satisfaction with
which specified users can achieve specified goals in a particular
environment.”
The key terms to note in this definition are:
• effectiveness: are users able to achieve their goals, fully and in the
manner expected, when using a product or system?
• efficiency: how much effort is required to use the product or system?
• satisfaction: was the user satisfied with the product or system?
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5. An introduction to usability
But note also the acknowledgement that systems and products are designed
for:
• a specified group of users
• to allow users to achieve specific goals
• a specific context or environment
This definition indicates that designers need to be aware of who the users of
their product or system will be. They must also understand the users’ goals
in using the product or system. And designers must also be aware of the
context in which users will use the system. There seems to be no place for a
“one size fits all” approach.
The 5 Es of usability
Whitney Quesenbery has suggested that a useful way to think about usability
is to consider the 5 Es of usability:
1. Effective
2. Efficient
3. Engaging
4. Error tolerant
5. Easy to learn
Effective
To be effective, a product or system must enable the user to complete the
task fully and accurately.
• Completeness: was the task fully completed? Were the user's goals
met?
• Accuracy: was the task completed successfully? Did the user get the
right or correct result? How well was the work done?
Efficient
To be efficient, a product or system must enable the user to complete the
task without too much physical or mental effort.
• Speed: was the user able to complete the task quickly? Was the
physical effort involved kept to a minimum?
• Effort: was the user able to complete the task without too much
mental effort?
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6. An introduction to usability
Engaging
To be engaging, the user must have a good and satisfying experience when
using the product or system.
• Pleasant: did the user have a pleasant experience when working on
the task?
• Satisfying: was the user satisfied by the way in which the application
supported her work?
Error tolerant
To be error tolerant, the product or system should minimise the chance of
errors and maximise the user’s ability to recover from any error that may
occur.
• Error prevention: did the user interface help users avoid making errors
or did poor design features result in mistakes? When errors occurred,
were they minor rather than major?
• Error recovery: if the user made an error, how hard did they have to
work to recover from it? Was it easy to recognise that an error had
occurred and find a way around it?
Easy to learn
To be easy to learn, the product or system must be predictable and behave
consistently.
• Predictability: was the user able to work with some certainty because
the user interface built on her previous knowledge?
• Consistency: was the interface consistent, so that once a user learnt
how to use part of the application, they were able to easily learn how
to use another part?
How “usability” is used
The term “usability” can be used in a variety of ways.
• Usability as an outcome or goal: websites and applications that are
usable
• Usability as a process: a design methodology or approach
• Usability as a set of techniques: usability testing, contextual enquiry,
heuristic evaluation. There are many techniques whose aim is to
improve usability
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7. An introduction to usability
• Usability as a philosophy: where improved usability is a value that
motivates the way in which products or systems are developed
The history of usability
The concept of usability comes from the field of human factors. Human
factors—sometimes known as ergonomics—has its roots in psychology and
originated in the United States military during World War II as a means of
ensuring that military staff could use sophisticated weaponry in the
conditions of war.
Human factors specialists study human beings and their interaction with
their environment. In particular, human factors is concerned with the
capabilities and limitations of the human mind and body, and how these
affect interactions with objects and conditions in the environment.
Human factors is now a multi-disciplinary field. Mark Chignall, drawing on
the work of Alphonse Chapanis, provides an overview of some of the
disciplines involved include:
• Psychology: human sensory capacities, human memory and cognitive
processes, and individual differences and their measurement.
• Anthropometry: the measurement of the physical features of people
as used in the design of seats, chairs, tables, computer consoles, car
interiors, aeroplane cockpits, and other workstations.
• Environmental medicine: environmental factors and their effects on
health and human performance.
• Engineering: electrical, mechanical, and chemical characteristics of
elements and systems and principles of design, construction and
operation of structures, equipment and systems.
• Operation research: quantitative methods for the analysis of the
performance of manpower, machinery, equipment, and policies in
government, military, or commercial spheres; the development of
models, such as queueing and allocation models for describing
operations
• Applied physiology: the vital process and the responses of these vital
processes to work, stress, and environmental influences.
• Statistics: used for summarising large amounts of data on human
measurements and human performance; also used to design sampling
schemes and experiments for human studies and performance
measurements.
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8. An introduction to usability
• Industrial design: design, colour, arrangement, and packaging to
combine functionality and an aesthetically satisfying appearance.
• Computing: primarily through human-computer interaction which is
concerned with human factors relevant to interactions with computers
and software applications.
The basic goals of human factors work includes:
• Meeting a range of basic operational and business objectives including
the reduction of errors, improved safety and improved system
performance, reduction in loss of time and equipment and increased
economy of production.
• Objectives bearing on reliability, maintainability, and availability
(otherwise known as RMA), and integrated logistic support (also known
as ILS). The goals would include increasing reliability, improving
maintainability, reducing personnel requirements and reducing
training requirements.
• Objectives affecting users and operators. Here goals would include
improving the working environment, reducing fatigue and physical
stress, increasing human comfort, reducing boredom and monotony,
increasing ease of use, and increasing user acceptance.
Notes
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9. An introduction to usability
Usability problems in our daily lives
Let's take a closer look at the design of some ordinary, everyday objects
that are difficult to use. These examples will help us delve into the causes
of usability problems and introduce some design principles from the field
of human factors.
Trapped between the doors
The first image shows a set of doors
connecting two buildings. I found the image,
and the story associated with it on a website
called “Bad Human Factors”, created by
Michael Darnell.
The story Michael tells is of two people who
were walking from one building to another.
They pulled open the first door but could not
open the second. Assuming it was locked
they returned to the first door, but now
could not open that one either. For a few
minutes they tried to signal someone to
come and help get them out. After a while
they realised they needed to push rather
than pull the doors.
The problem arose because both sets of doors have handles on each side.
Handles imply or afford pulling. The problem could have been prevented if
flat plates had been used on the side of the door that required a push to
open, leaving handles on the side of the door that opened by pulling.
If the designer of the doors had been aware of affordances and constraints,
and used them to advantage, the design of the doors would have been more
usable.
In his book, The Design of Everyday Things, Donald Norman says that
affordances are the actual or perceived properties of an object that
determine how the object could be used. For example:
• a chair affords sitting
• a button affords pushing
• slots afford inserting things into them
• knobs afford turning
When affordances are taken advantage of, users know what to do just by
looking: no picture, label or instruction is required.
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10. An introduction to usability
Constraints, on the other hand, are properties of an object that limit the
way the object can be used in order to make its mode of use obvious.
For example, the holes in the handle of a pair of scissors provide constraints
for use. The small hole suggests only one finger will fit, while the larger
hole suggests more than one.
Jigsaw puzzles are also an excellent example of using constraints. The shape
of the piece, and the colours and patterns printed on it, provide constraints
for where it can be placed.
In the case of our example doors, the use of flat plates on the sides of the
doors that required pushing would have provided a constraint so that it was
obvious to users that they must push the door.
How do you open the fridge?
This refrigerator has no handle on the front, but
recessed handles on the side.
It was purchased for use in a staff room, and new
staff members commonly had the same problem
using it. After seeing that there were no obvious
handles on the front of the fridge, they would
locate the recessed handles on the side and try to
open the fridge. When it didn't budge, they often
assumed it was sealed tight and so pulled even
harder—some of the stronger ones managing to
move the fridge, but not open the door.
What most people failed to notice was that there
are two sets of handles, one on each side. They
were put there to allow the door to be hinged from
either side, depending on the layout of the room
where the fridge was located.
Leaving both sets of handles visible after
installation caused confusion. Users were able to,
and often did, make mistakes when trying to open
the fridge.
This is a good example of the failure to use
constraints to improve usability. While the
designers intended to provide flexibility by
allowing the door to be hinged on the side most
suitable for its context of use, they failed to
provide constraints to ensure that users only
attempted to open the door from the appropriate
side.
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11. An introduction to usability
The case of the mistaken urinal
This is a photo of a toilet in a
restaurant. Can you guess what
the object in the right-hand
corner is?
The small handmade sign over
the top of it (indicated by the
arrow) reads "this is a mop sink"
suggesting that it has been
mistakenly used as a urinal.
The problem with this design is
to do with its context of use.
Men are accustomed to finding urinals in public toilets. Although the design
of the mop sink might be perfectly suitable if it were placed in another
location (in a cleaner's supply room, for instance), given its location in a
toilet, its intended purpose is easily mistaken. In this case, an alternative
design that made the purpose of the object more obvious, would have
solved the problem.
How do I turn on the computer?
This is a rather humiliating story that I am prepared to tell to highlight
another important human factors design principle—visibility.
Several years ago I started a new
job. On my first morning in the
office I discovered that I had the
choice of using an antiquated old
PC or an almost new Macintosh
G3. Although I'd never used a Mac
before, I was more than keen to
give it a try, especially as it had a
beautiful 21 inch monitor
attached. However, I couldn't
figure out how to turn it on.
There were no obvious buttons on
the case, front or back.
Risking damage to my yet-to-be
established reputation, I knocked
on the door of my colleague and
asked if he could help me turn the
machine on. He couldn't find the
ON button either.
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12. An introduction to usability
Eventually, one of us accidentally hit the key on the
keyboard that brought the machine to life. We didn't
notice which one it was, and had trouble finding it again a
second time. It turned out to be the apple (or command)
key. Incidentally, many Windows users say they have had a similar problem
when trying to use a Macintosh for the first time.
How fast am I travelling?
Here is another example of the problem of visibility.
Many cars have speedometers
and tachometers. There is no
standard for placement of
these instruments, so the
speedo might be on the left
side in one car and the right in
another.
In the case of the picture above, what makes identification of the speedo
more difficult is that the same numeric scale is used for both the speedo
and the tacho.
Using a different scale, and/or making the speedo larger and more
prominent would make the more important of the instruments more visible.
Did I send that fax?
A few years back our office purchased a
new multi-function printer, copier and
fax machine that looked just like the one
at right. I'd been using it without
problems for a few weeks for printing
and copying, but my first experience at
sending a fax was not a happy one.
I'd just pressed the send button when I
was interrupted by a colleague who
walked into the room. We had a short
chat and afterwards, I had no idea of
whether or not the fax had been sent. I couldn't recall hearing the machine
dialling the number and nothing on the LCD display screen indicated what
had gone on.
So I tried again. I listened for a dialling sound but there was none, and again
there was no message on the LCD screen (pictured below).
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13. An introduction to usability
Not easily deterred, I tried a third
time. This time I noticed a small
green light marked 'COMM' go on
(indicated by the black arrow in
the photo). There was still no
message to indicate that the fax
had been sent, but I was a little
more confident that it was at least
trying to send it.
It wasn’t until I returned to my
office a short time later that I
knew the fax had been sent. The person to whom I was trying to send it,
telephoned to assure me that they had received it—they had received all
three copies, thank you very much!
This incident illustrates another design problem: there was no feedback
about what the machine was doing. Feedback tells the user about the result
of an action. For example, when we turn a car steering wheel, the car
immediately starts turning. We get immediate feedback about the results of
our action. Some other examples of feedback are:
• the tone made when you push numbers on a telephone keypad
• the 'connecting to site name' that appears in your web browser status
bar when you click on a hyperlink
• the clicking sound and flashing dashboard light that shows you've
turned on your car's turn indicator.
Which knob controls the front left burner?
The picture at left is of a four-burner
cooktop. The controls for the burner are
vertically arranged on the right. I have a
cooktop with a similar layout at home. My
partner and I often find that we turn on the
wrong control, despite the fact that we’ve
been using this same cooktop for many
years.
When I tell this story to other people, they
often confess to having a similar problem.
Now look at the second cooktop. Do you
think people would have the same
problems identifying the correct knobs
using something designed like this?
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14. An introduction to usability
The problem with the first design is poor mapping. Mapping refers to the
relationship between things, in this case between the layout of the controls
and the layout of the burners. The relationship is not obvious. The upper
control may turn on the top left burner, or the top right. Users would have
to read the labels on the controls to figure it out.
In the second design, the layout of the controls matches the layout of the
burners, and it is immediately obvious which control operates which burner.
No labels are needed.
Where designers take advantage of physical analogies or cultural standards
to provide immediate understanding of how things work, Donald Norman
refers to the mapping relationship as “natural mapping”.
Steering a car is an example of the use of natural mapping. We turn the
steering wheel clockwise to the right to turn right, and anti-clockwise, or to
the left, to turn left. The mapping relationship is natural and so is easy to
remember.
The well-trodden path
This picture shows a path worn in the grass
between two paved paths at the end of a
pedestrian crossing. There is a sign erected near
the start of the worn path that reads
"Landscape Preservation. Please use sidewalks".
This is an example of a design (the original
location of the paths) and a design solution (the
erection of a sign) that both ignore human
behaviour.
Making a path in the right place instead of
wasting money on a sign that is unlikely to
motivate a change in human behaviour, would
have been a better use of resources.
Can’t get a grip
The next photo shows a wash
basin in a designer hotel. The
smooth tap knobs make operating
the taps very difficult with soapy
hands.
This design fails partly because of
a failure to realistically consider
the context of use, but also
indicates a failure to design for
human behaviour. We don’t all
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15. An introduction to usability
manage to get the water pressure and temperature right before we put soap
on our hands. Some of us need to make adjustments while we're washing.
What happens when a heavy door
has a handle in the middle?
The next photo shows a fancy restaurant door. It is
made of heavy-duty glass, and the restaurant is
visible through the top half of the door. But, the
handle is located in the middle of the door, rather
than on the side. This makes the door very difficult
to open for some people because it is not possible
to get good leverage.
There is a good reason for the design convention
for door handles—positioning the handles on one
side makes it easier to open the door.
Often, design practices become conventions simply
because they work well. Breaking design
conventions often leads to products or systems that
don't work so well.
Here is another example.
How do I get water from the tap?
This outdoor tap works by lifting the handle. However, it looks like a pump-
action device, and so many people thought that they had to pump the
handle in order to get the water to flow.
Again, using a more conventional design for the tap would have made it
easier for people to figure out how to use it.
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16. An introduction to usability
Discussion:
What design problems have you encountered with everyday objects?
In your examples, can you identify any design principles that the designer
has not followed?
Notes
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