1. Southern Cross University 1 CADUI'96 - 5-7 June 1996 - FUNDP Namur Investigating Layout Complexity Tim Comber Dr. John Maltby Centre of Computing Southern Cross University LISMORE ( Australia)

2. Southern Cross University 2 CADUI'96 - 5-7 June 1996 - FUNDP Namur The importance of screen design Acceptance and performance influenced by presentation Successful screen design is essential to most interactive systems Most new computer systems use some form of GUI. Few empirical studies relating to modern, bit- mapped screens

3. Southern Cross University 3 CADUI'96 - 5-7 June 1996 - FUNDP Namur Guidelines say: Keep the interface simple and well-organised –Does this apply to a GUI? –Are simple interfaces the most usable? –And, how can the designer know that a simple interface has been achieved?

4. Southern Cross University 4 CADUI'96 - 5-7 June 1996 - FUNDP Namur Shannon’s Formula K = a positive constant n = number of event classes pi = probability of occurrence of the ith event class

5. Southern Cross University 5 CADUI'96 - 5-7 June 1996 - FUNDP Namur The communication process: Consists of n classes of event An event is the transmission of a specific “unit” of information. If letters of the alphabet are the communication units then: –n = 26

6. Southern Cross University 6 CADUI'96 - 5-7 June 1996 - FUNDP Namur Entropy entropy is a measure of the disorder of a system –identical to that of entropy in statistical mechanics

7. Southern Cross University 7 CADUI'96 - 5-7 June 1996 - FUNDP Namur Entropy in the case of two possibilities with probabilities, p and (1 - p) Entropy is a maximum if events in all classes occur with equal probability. ie when there is most uncertainty Entropy is zero when one class of event becomes certain, ie when there is no uncertainty

8. Southern Cross University 8 CADUI'96 - 5-7 June 1996 - FUNDP Namur Implications of the theory communication includes speechmusicballet Information can be defined as: –a measure of the freedom of choice when selecting a binary event to send down a communication channel.

9. Southern Cross University 9 CADUI'96 - 5-7 June 1996 - FUNDP Namur Diagram of a GUI communication system CPUMonitorEyesBrain Noise MessageGUIImageMessage A GUI can be viewed as a communication system between CPU and user

10. Southern Cross University 10 CADUI'96 - 5-7 June 1996 - FUNDP Namur Information Information is proportional to log 2 of the possible meanings

11. Southern Cross University 11 CADUI'96 - 5-7 June 1996 - FUNDP Namur Information and entropy Entropy describes the amount of uncertainty in the progress of a message. When the user begins, –any interaction object can be chosen, –then probability can be used to indicate the next choice –dependent on the order of prior objects in the sequence. In a highly organised transmission the amount of information (entropy) is low and there is little randomness or choice.

12. Southern Cross University 12 CADUI'96 - 5-7 June 1996 - FUNDP Namur Redundancy Redundancy is given by: –R = 1 - H/H MAX where –H = entropy R is the amount of the message that is determined by the statistical rules of the message language and is not due to free choice.

13. Southern Cross University 13 CADUI'96 - 5-7 June 1996 - FUNDP Namur Redundancy and the English language Weaver points out that about 50% of the English language is redundant, 1.Omit much words make text shorter. 2.Thxs, wx cax drxp oxt exerx thxrd xetxer, xnd xou xtixl maxagx prxttx wexl. 3.Thng ge a ltte tuger f w alo lav ou th spce.

14. Southern Cross University 14 CADUI'96 - 5-7 June 1996 - FUNDP Namur Redundancy and interfaces A command language interface is a low entropy interface much like the third example for the English language. In contrast, GUI’s have a much higher redundancy.

15. Southern Cross University 15 CADUI'96 - 5-7 June 1996 - FUNDP Namur Applied to typography - Bonsiepe Entropy is a measure of the disorder of the system. System order: –objects classified by common widths and common heights distribution order: –objects classified by distance from the top and left of page. The proportion of objects in each class determines the complexity of the layout.

16. Southern Cross University 16 CADUI'96 - 5-7 June 1996 - FUNDP Namur Technique Compared two versions of a printed catalogue. It was found that the new version was 39% more ordered than the original version. Offers a justification for grid based layout.

17. Southern Cross University 17 CADUI'96 - 5-7 June 1996 - FUNDP Namur Applied to computer screens - Applied to computer screens - Tullis Structured layout (minimising layout complexity): –increases the user’s ability to predict the location of items –thus improves the viewer’s chance of finding the desired information. A useful usability metric? –Did not predict time to find information. –but, Important predictor of users’ rating of the usability of screens.

18. Southern Cross University 18 CADUI'96 - 5-7 June 1996 - FUNDP Namur Aim of the research Develop a metric for evaluating object placements in a graphical user interface based on complexity theory “Where is the best place to put things”. Provide immediate feedback on the layout quality of the GUI.

19. Southern Cross University 19 CADUI'96 - 5-7 June 1996 - FUNDP Namur Optimum Complexity Usability Complexity It is hypothesised that there is a trade off between usability (U) and complexity C with a relationship of the form U = f(C) where U is a maximum for some intermediate value of C

20. Southern Cross University 20 CADUI'96 - 5-7 June 1996 - FUNDP Namur Initial investigation Apply Bonsiepe’s technique to thirteen different Microsoft Windows applications Large variation in complexity figures for the thirteen displays Possible to apply manually but not efficient or accurate

21. Southern Cross University 21 CADUI'96 - 5-7 June 1996 - FUNDP Namur 23.68 173.35 285.61 1571.98

22. Southern Cross University 22 CADUI'96 - 5-7 June 1996 - FUNDP Namur Screen complexity and user preference Bonsiepe and Tullis indicated that less complex is better –User’s should agree –Subjects were asked to sort the screen prints from best design to worst design, with no ties. Results –Subjects had a common interpretation of “goodness” of design. –However, the distribution of the results was unexpected. –A greater preference for the more complex screens.

23. Southern Cross University 23 CADUI'96 - 5-7 June 1996 - FUNDP Namur Evaluating usability of screen designs Usability consists of: –effectiveness, learnability, flexibility, and attitude Visual Basic (VB): –Information about the dimensions and positions of objects. –Track the user’s progress with a task, keeping a record of each event and time taken. Pilot application, Launcher

24. Southern Cross University 24 CADUI'96 - 5-7 June 1996 - FUNDP Namur

25. Southern Cross University 25 CADUI'96 - 5-7 June 1996 - FUNDP Namur Screen Layouts Four different screen layouts were designed, each with a different complexity score

26. Southern Cross University 26 CADUI'96 - 5-7 June 1996 - FUNDP Namur Screen 1 - Complexity equals 156

27. Southern Cross University 27 CADUI'96 - 5-7 June 1996 - FUNDP Namur Screen 2 - Complexity equals 170

28. Southern Cross University 28 CADUI'96 - 5-7 June 1996 - FUNDP Namur Screen 3 - Complexity equals 186

29. Southern Cross University 29 CADUI'96 - 5-7 June 1996 - FUNDP Namur Screen 4 - Complexity equals 228

30. Southern Cross University 30 CADUI'96 - 5-7 June 1996 - FUNDP Namur Procedure Subjects were requested to complete the same task for each screen. Asked to indicate their preferences for the different screens. Recorded: –Time it took users to complete each step in a task –Any errors.

31. Southern Cross University 31 CADUI'96 - 5-7 June 1996 - FUNDP Namur Summary UsabilityScr. 1Scr. 2Scr. 3Scr. 4 Complexity156170186228 Error-free 36% 79% 86% 71% Time354290276293 Rating 4 7 16 0

32. Southern Cross University 32 CADUI'96 - 5-7 June 1996 - FUNDP Namur Conclusions from pilot Differences in usability between screens differing in complexity. VB proved useful tool for: –calculating complexity –collecting data about the user’s interaction

33. Southern Cross University 33 CADUI'96 - 5-7 June 1996 - FUNDP Namur Implications for GUI design There are two groups that require a method of evaluating GUI applications. 1.Designers choosing between competing layouts. 2.Comparing different applications for design quality. Give feedback to the designer during design: –layout complexity metric –Kim’s symmetry and balance –Sear’s layout appropriateness Designers can modify their design “on-the-fly”

34. Southern Cross University 34 CADUI'96 - 5-7 June 1996 - FUNDP Namur Extensions to Launcher More screens More tasks Wider cross-section of users Extra metrics will also be added –including Sear’s “layout appropriateness” –percentage white space –Kim’s balance