Sep 5 - Whitehead, Evaluating Web Page and Web Site Usability

Evaluating Web Page and Web Site Usability.
Christopher C. Whitehead. Columbus State University, 4225 University Avenue, Columbus, GA 31907. 1-706-565-3527 whitehead_christopher@colstate.edu

ACM SE’06, March, 10-12, 2006, Melbourne, Florida, USA

ABSTRACT
As the number of Web sites continue to increase, so too does the importance of Web page/Web site usability. This paper describes what constitutes Web page/Web site usability and how it can be measured.

Why is usability important?
As Nielsen states, "Usability rules the Web. Simply stated, if the customer can't find a product, then he or she will not buy it" [5].
In this sense, usability is an extremely important aspect of individual Web page and overall Web site design, particularly for the business-oriented Web site.
In discussing e-commerce Web sites, Shacklett asserts that, "Twenty-eight percent of Web site transactions result in consumer failure and frustration....Six percent of users who leave a Web site in frustration say they won't return to the site or patronize the company” [7].
If usability is left unconsidered, then a business is likely to lose customers and miss out on profit opportunities--negatively impacting the cornerstones of any successful business.

WHAT IS WEB PAGE/SITE USABILITY?

Based on the International Standards Organization (ISO) definition of usability, Powell defines Web site usability as "the extent to which a site can be used by a specified group of users to achieve specified goals with effectiveness, efficiency, and satisfaction in a specified context of use" [6].
Note that this definition applies equally well to Web page usability. It also implies that usability is user and task dependent, as well as being related to how well the user is able to accomplish what they set out to do, how efficiently the user can do this, and how satisfied the user is during and after the process.

..Jakob Nielsen's usability guidelines for determining the usability of a Web site [6]:
• Learnability--How easy it is to learn to use?
• Rememberability--How easy it is to remember how to use?
• Efficiency of use--How much work does it require the user to do?
• Reliability in use--Does it work correctly and does it help users perform tasks correctly?
• User Satisfaction--Is the user generally satisfied as a result of using the site?

..McLaughin and Skinner break usability down into six related but distinct components [4]:
• Checkability: The system has or allows checks that ensure the correct information is going in and going out of it.
• Confidence: Users have confidence both in their capability to use the system and in the system itself.
• Control: Users have control over the operation of the system, particularly of the information fed into and out of the system.
• Ease of Use: The system is easy to use.
• Speed: The system can be used quickly.
• Understanding: The system and its outputs are understandable.

In general then, usability is potentially complex and wide ranging,
but clearly "user-centered." In evaluating usability, it may be possible to measure each of these components separately or in combination using some form of metric or measure.

USABILITY TESTING

Battleson et al. claim that usability testing is the most effective way to asses a site's usability [1]. They go on to specify three categories of usability testing: inquiry, inspection, and formal usability testing.

Inquiry usability testing requests information from the user and includes the use of focus groups, interviews, questionnaires, and surveys.

Inspection usability testing includes heuristic evaluation and cognitive walkthroughs. According to Dickstein and Mills, “Heuristic evaluation is a systematic inspection of a user interface to examine if the design is in compliance with recognized usability” [2]. This typically involves checking the site “against a checklist of heuristics, or design principles” [1]. Cognitive walkthroughs involve enlisting the use of individuals “to accomplish typical user tasks with a given interface” [1].

Under formal usability testing, a formal set of tasks and goals are defined and users are observed while performing these tasks. According to Battleson et al., formal usability testing involves the following: “(1) the goal is to improve the usability of the interface; (2) testers represent real users; (3) testers perform real tasks; (4) user behavior and commentary are observed and recorded; and (5) data are analyzed to recognize problems and suggest solutions” [1].

Ivory et al. also report that simulation has been used to effectively evaluate web sites by automating the implementation of usability testing [3]. Using this methodology, user behavior is mimicked in a controlled environment or through computer simulation without actual users.

Determining the Number of Users to Involve in the Testing
In performing usability testing, Battleson et al. claim that in a homogenous user testing group, as little as five users are needed to ascertain a large percentage of the most critical errors [1].
In comparison, Dickstein and Mills found that eight to twelve users was sufficient enough to determine problems with a Web site’s usability [2]. However, they also claim that by the fifth user, they were able to determine whether the tested feature was either a problem or a success.

USABILITY METRICS

Usability metrics are measures of a particular aspect of a Web page or Web site that has an impact on usability.
In today's environment, there are numerous proposed metrics.

In performing quantitative usability testing, Ivory, et al. suggest the following Web page metrics as the most important in evaluating usability [3]:
• Word Count--Total words on a page
• Body Text %--Percentage of words that are body vs. display text (i.e., headers)
• Emphasized Body Text %--Portion of body text that is emphasized (e.g., bold, capitalized or near !'s)
• Text Positioning Count--Changes in text position from flush left
• Text Cluster Count --Text areas highlighted with color, bordered regions, rules or lists
• Link Count--Total links on a page
• Page Size--Total bytes for the page as well as elements graphics and stylesheets
• Graphic %--Percentage of page bytes that are for graphics
• Graphics Count--Total graphics on a page (not including graphics specified in scripts, applets and objects)
• Color Count--Total colors employed
• Font Count--Total fonts employed (i.e., face + size + bold + italic)

Ivory et al. found six metrics to be of most importance: text cluster count, link count, page size, graphics count, color count, and reading complexity [3].

CONCLUSION
In summarizing the importance of Web page/Web site usability, Nielsen states, "Usability has grown dramatically in importance for web-based companies because of an inversion in the relationship between user experience and the ability to separate customers from their money" [5]. This inversion is due to the way in which the Web works in that users are able to experience a company before they commit to either making a purchase or going elsewhere. This makes the user all-important for those businesses that expect to profit from the Web. And, as a result, as Dickstein and Mills claim, “Usability testing methods, by their very nature, keep the user in the forefront” [2]. It is because of this "user-centered" approach that evaluating the usability of Web pages and Web sites is so vitally important to today's businesses.

References that I may want to read further in future:
[3] Ivory, M. Y., Sinha, R. R., & Hearst, M. A. Empirically Validated Web Page Design Metrics. ACM SIGCHI'01, 2001.
[5] Nielsen, J. Designing Web Usability: The Practice of Simplicity. Indianapolis, IN: New Riders Publishing, 2000.
[6] Powell, T. A. Web Design: The Complete Reference. Berkeley, CA: Osborne/McGraw-Hill, 2000.
[7] Shacklett, M. Gauging Web site performance. Credit Union Magazine, 67, 6, 2001, 60-62.