. Using examples describe the stages of Donald Norman’s model of Interaction[5 Marks]b. List and discuss briefly Nielsen’s ten heuristics [5 Marks]c. The focal point of Gestalt theory is the idea of “grouping,” or how we tend to interpret a visualfield or problem in a certain way. Explain briefly the four main factors that determine grouping.[4 Marks]d. Interface evaluation is the process of assessing the usability of an interface and checkingwhether it meets user requirements. Briefly explain any two evaluation technique.[4 Marks]e. Discuss four characteristics of a usable system [ 2 Marks]

a. Donald Norman’s model of Interaction consists of seven stages: Forming the Goal, Forming the Intention, Specifying an Action, Executing the Action, Perceiving the System State, Interpreting the System State, and Evaluating the Outcome. For example, if a user wants to send an email, the goal is to send the message, the intention is to use an email service, the action is to write and send the email, the execution is the actual sending of the email, the system state is the sent message, the interpretation is understanding the message has been sent, and the evaluation is the satisfaction of the message being sent.

b. Nielsen’s ten heuristics include: Visibility of system status, Match between system and the real world, User control and freedom, Consistency and standards, Error prevention, Recognition rather than recall, Flexibility and efficiency of use, Aesthetic and minimalist design, Help users recognize, diagnose, and recover from errors, and Help and documentation.

c. The four main factors that determine grouping in Gestalt theory are: Proximity (objects close to each other are perceived as a group), Similarity (similar objects are perceived as a group), Continuity (lines are seen as following the smoothest path), and Closure (objects grouped together are seen as a whole).

d. Two evaluation techniques for interface evaluation are Heuristic Evaluation, where a set of heuristics are used to identify usability problems in the user interface design, and Cognitive Walkthrough, where the ease of learning of a system by exploration is evaluated.

e. Four characteristics of a usable system are: Learnability (how easy it is for users to accomplish basic tasks the first time they encounter the design), Efficiency (once users have learned the design, how quickly they can perform tasks), Memorability (when users return to the design after a period of not using it, how easily they can reestablish proficiency), and Errors (how many errors users make, how severe these errors are, and how easily they can recover from the errors).