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Concepts of (HCI) Human Computer Interaction

Selecting Colors during Web Design

Use this element to create strong contrast between text and background. If this item is used behind blocks of text of a certain type of content, it should be consistent throughout.
  1. Text: Putting this element in a small size may prohibit the visually impaired from using your site. Large size may indicate amateurishness.
  2. White/empty space: This element is important because a page that is completely filled will overwhelm users and obscure the important content.
  3. Animations: These may help to build interest for the page, but can easily be overdone. Use sparingly.
  4. Graphic size and download times: Large file sizes will cause users to become frustrated with delays, potentially leaving the site early.
  5. Text length: This element should be considered because most people prefer concise content for shorter reading times on the Web.
  6. Chunking: Use this strategy to keep each page manageable. Long text may need to be segmented, given headings, and put on separate pages.
  7. Scannability: Consider this feature because people prefer to glance over a page to assess its usefulness before reading it all. Build in signposts like headings and key words, to indicate the topic of your content.
  8. Scrolling or fixed: This will determine the length of page content due to some reluctance to use the mouse or down arrow to move down the page.
  9. Language style and tone: The manner and feel of the written content of the site, adjusted for the target audience group.
  10. Proofreading: Checking accuracy of the written content to avoid simple typographical or factual errors.

Usability as a High Level Quality Objective

Guidance on Usability
The objective of designing and evaluating for usability is to enable users to achieve goals and meet needs in a particular context of use. ISO 9241-11 explains how usability can be specified and evaluated in terms of user performance and satisfaction. User performance is measured by the extent to which the intended goals of use are achieved (effectiveness) and the resources such as time, money or mental effort that have to be expended to achieve the intended goals (efficiency). Satisfaction is measured by the extent to which the user finds the use of the product acceptable. ISO 9241-11 also emphasises that usability is dependent on the context of use and that the level of usability achieved will depend on the specific circumstances in which a product is used. The context of use consists of the users, tasks, equipment (hardware, software and materials), and the physical and organisational environments which may all influence the usability of a product (see Figure 4-3).

Figure 4-3: Usability framework
ISO 9241-11 was developed in close conjunction with the MUSiC project. The user-based MUSiC methods and tools provide a practical implementation of the principles of the standard. The Usability Context Analysis Guide provides a procedure for documenting the context of use and context of evaluation. The Performance Measurement Method (Bevan and Macleod, 1994) provides a reliable and repeatable method for measuring effectiveness and efficiency and diagnosing usability problems. SUMI (Kirakowski, 1995) enables different aspects of user-perceived usability to be measured and areas of difficulty to be pin-pointed. Cognitive workload can be measured (Wiethoff et al 1993) as a means of predicting over- or under-loading of the user.