Empirical assessment of patterns and guidelines for web design.

The phenomenal and explosive growth of the internet makes the need for proven, dependable approaches to interaction and interface design more important. Efficient and effective design methods are needed, complete with appropriate techniques and tools that support designers in developing and delivering usable systems. Knowledge and experience significantly contribute to producing better design products. Traditionally, design knowledge and experience is conveyed in the form of guidelines. In recent years, there has been a growing interest in design patterns as an effective way of capturing and communicating design knowledge.This thesis contributes to the ongoing debate concerning the benefits of patterns, as they are contrasted to another form of design guidance in the field of web design. The thesis investigates the effect of patterns and guidelines in the development of skills of students acting as novice designers. The aim is to empirically test how patterns and guidelines affect novice designers in creating and evaluating a web site. Its motivation is to advance the understanding of how novices employ and value patterns and guidelines after being introduced to usability issues with the help of these tools. Moreover, this study also highlighted participants' attitudes and preferences towards patterns and guidelines.Three experiments were conducted for the purposes of this research. Each experiment contributed significantly to the understanding of how the next experiment should be carried out, and the findings and lessons learned at each stage have extensively influenced the next stage. Both quantitative and qualitative methods were used to collect and analyze data. Detailed descriptions of the experimental procedures are provided and give insights into the use of patterns and guidelines by novices. The results indicate that patterns and guidelines can successfully communicate usability principles and knowledge to novice designers and can affect the design and evaluation skills of participants.The difference in the overall scores in the design task between the two groups, using subjective and objective metrics, is statistically significant with the patterns group performing better. Results from the design task and the interviews suggest that compound patterns are inferior to simple patterns and do not create a clear picture of all the usability issues involved to novice designers. There is no significant difference between the performances of the two groups in the evaluation task. However, if a comparison is made using difficult to identify errors the patterns group perform significantly better than the guidelines group.The overwhelming preference for a particular format in presenting guidance is patterns even by the participants trained with guidelines. Links to other patterns within the pattern collection and pattern names are not appreciated by participants, although guideline titles are considered to provide useful information and guidance. Patterns are considered by participants as better tools to introduce design principles to novices while guidelines are perceived as tools for more experienced designers. At the same time patterns are suggested as a useful pedagogic tool for teaching.Overall the study represents an important fist step towards comparing patterns with another similar tool for providing guidance to designers. Development of original experimental designs was required since no similar studies have been conducted. The work of this thesis can serve as a starting point for more thorough assessment of design patterns and their potential benefits in designing more usable interfaces and in education as a tool for knowledge transfer and training.