Usability -1h

Learning Outcomes

• Readability

• Navigation

• Accessibility to challenged people

• Testing to ensure that the changes to the site have indeed been improvements..

Definitions of Usability Productivity: How fast or efficient can the user be with the

help of this system? Learnability: How easy is it for a newcomer to learn the

system? Memorability: When a user returns to the system, must

they relearn it or will they be able to remember skills they learnt first time round.

Error frequency: How easily can the average user make mistakes?

Satisfaction: Does the system make the user feel inadequate? Do they enjoy using it?

More Definitions

The capability of the software product to be learned, used, and attractive to the user, when used under specified conditions (ISO/IEC 9126-1)

The extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use (ISO 9241-11).

The ease with which a user can learn to operate, prepare inputs for, and interpret outputs of a system or component (IEEE Std. 610.12)

Readability

Categories:

• Titles

• Page Length

• Page Layout

• Text presentation

• Reading

• Graphics

Titles

• Use the <TITLE> tag

• Give a good self-explanatory main title– Many users will have arrived via search engines– introduce the page so as to reorient these

visitors

• Use subheadings informatively– 79% of web users scan pages– scanners focus on titles rather than text

Page Length

• Bailout rate is proportion who leave page before it has completely downloaded– Average background figure for bailout rate is

about 8%– This climbs to around 27% for a download time

of 8 seconds (around 40 k-bytes)

• Many users don't bother to scroll scrolling pages

Page Layout

• Line up the various elements vertically.

• Background colours can lead the eye from one important point to another.

• The impatient surfer may not want to scroll.

• It is important to be consistent

• You don't need to sacrifice readability, just to improve visual style.

Text presentation

• Don’t use more than two point sizes on the page.

• Text any smaller than ten-point is difficult to read; I aim for twelve-point.

• Try to use a readable typeface.

• Avoid the over-use of ornate decorative fonts.

Reading

• Use a restricted vocabulary.• Too much solid text could frighten a user away.• Write scannable text:

– Subtitles self-explanatory– Make link-text say something pithy– Gems within the text could be emboldened

• Paragraphs should express only one idea

Graphics

• Some will not be using monitors at all.

• Use ALT text.

• Don’t use graphics as links

• Make links look like links: "mine sweeping"

• Don’t hide the meaning of an image link until it is rolled over by the cursor.

Consistent Navigation Aids

• Second nature

• Found in conventional places

• To where expects to go

• To where wants to go

• Breadcrumbs

Text-based Navigation

• Use well chosen words

• Images are ambiguous

• Some will have images switched off

• Some browsers don’t show images

• Use ALT text and/or a caption which is also a link

Navigation and Links

• Group your links into sensible groupings

• Put them where people expect them

• Sometimes more than one clump of links, in different zones of the page

• (But also contextual navigation)

Navigation Map Design

• Where am I?

• Where can I go next?

• How can I recover from an error?

• The three-click rule

• Put important information high up the navigation hierarchy

Accessibility: colour

• Some won’t be using monitors

• Fair number are colour blind (some don’t know it yet)

• Can’t rely on client’s hardware

Accessibility: Alternative Formats

• Some can’t perceive:– Graphics– Video– Sound

• …So offer a text alternative!

• Use ALT tag

• Give text descriptions of videos etc

Accessibility: User Control

• Slow readers have difficulties with:– Blinking text– Marquee– Timed slide shows

• Give them the option of control

Testing

Categories:• Usability inspection• Group Walkthrough• User Testing• Diary Studies• Server Statistics

Usability inspection

• Expert Critique =

• Trained professional goes through the site.

• List of heuristics

• Makes a note of any problem

• Five independent experts better

• Alternatively, ordinary person with a comprehensive checklist

Group Walkthrough

• Group of non-designers

• Try to carry out specified tasks.

• people already involved in the conceptual design (e.g. users, directors, union representatives and office workers).

• Facilitator suggests guidelines or faults to look out for

User Testing

• Watch individual user do tasks

• Reassure that test is of site and not of them

• Mistakes are probably due to imperfect site design

• Tasks deliberately made slightly general

Diary Studies

• Some users are asked to make notes over a long period.

• Not possible to see what they are actually doing

• Long-term technique

Server Statistics

• Which are your most/least popular pages

• How long do people spend reading?

• Success ratio of viewers to purchases

• Where do they bail out?

• What routes do they take through the site?

• Onto which page do they generally arrive?