Evaluation of User Interface Design

1. Evaluation of User Interface Design 4. Predictive Evaluation continued Different kinds of predictive evaluation: Inspection methods Usage simulations Heuristic evaluation Discount usability evaluation Walkthroughs Modelling: The keystroke level model

2. Evaluation of User Interface Design 4. Predictive Evaluation continued Inspection methods Inspection of technology aspects by specialists who know about both the users and the technology. Usually, the specialists focus on the interaction dialogue between individual users and a system. The main purpose is to generate a list of usability problems.

3. Evaluation of User Interface Design 4. Predictive Evaluation continued 2. Usage simulations Expert review of the system to find out about possible usability problems. The reviewers simulate the behaviour of less experienced users and try to anticipate their usability problems.

4. Evaluation of User Interface Design 4. Predictive Evaluation continued 2. Usage simulations continued This is typically seen as very effective, because a small number of reviewers can identify a range of usability problems for which a much greater number of real users would be required otherwise. The expert reviewers can also give quick advice on what to do better.

5. Evaluation of User Interface Design 4. Predictive Evaluation continued 3. Heuristic evaluation Expert review where the inspection is guided by a set of high-level heuristics, e.g. * Use simple and natural dialogue/minimise user‘s memory load * Provide feedback, shortcuts, good error messages and clearly marked exits * Prevent errors in the first place

6. Evaluation of User Interface Design 4. Predictive Evaluation continued 4. Discount usability evaluation ...is intended for developers with few resources in terms of time, money, expertise, e.g. small companies. The discount usability evaluation is a mixture between empirical usability testing and heuristic evaluation.

7. Evaluation of User Interface Design 4. Predictive Evaluation continued 4. Discount usability evaluation continued In its first part, this method typically involves the construction of small scenarios (e.g. paper mock-ups, HyperCard simulations) that are tested with informal Think Aloud Protocols. On the basis of these results, the scenario is changed and tested again.

8. Evaluation of User Interface Design 4. Predictive Evaluation continued 4. Discount usability evaluation continued In its second part, this method typically involves testing the scenario using the heuristic evaluation method that was mentioned in the previous point. Only a small number of reviewers are involved in the Discount usability evaluation.

9. Evaluation of User Interface Design 4. Predictive Evaluation continued 5. Walkthroughs ...are aimed at discovering problems very early on so that they can be removed. They involve carefully defined tasks, e.g. a walk through cognitive and operational activities that are required to get from one screen to the next.

10. Evaluation of User Interface Design 4. Predictive Evaluation continued 5. Walkthroughs continued First, experts will specify the exact task, the context and any assumptions about the possible users. They then carefully walk through the task by reviewing the necessary actions to achieve the task and by predicting the most likely user behaviour and problems.

11. Evaluation of User Interface Design 4. Predictive Evaluation continued 5. Walkthroughs continued A Walkthrough resembles a review in many aspects, except that a more detailed prediction of user behaviour is required for the walkthrough.

12. Evaluation of User Interface Design 4. Predictive Evaluation continued 6. Modelling: The keystroke level model Modelling is somewhat more remote from the actions of real users. It requires a specification of the system‘s functionality and a task analysis (= a list of all the proposed user tasks with a breakdown of each task into its components).

13. Evaluation of User Interface Design 4. Predictive Evaluation continued 6. Modelling: The keystroke level model continued In this respect, a number of analytic methods have been developed, of which the keystroke level model is just one simple example (though it is one of the most well-known).

14. Evaluation of User Interface Design 4. Predictive Evaluation continued 6. Modelling: The keystroke level model continued The keystroke level model deals with very short tasks, e.g. single commands, and measures task performance times of expert users to give the designer an idea of the minimum task performance time.

15. Evaluation of User Interface Design 4. Predictive Evaluation continued 6. Modelling: The keystroke level model continued The keystroke level model does not consider novice users, who are prone to make errors. The model assumes expert error-free performance.

16. Evaluation of User Interface Design 4. Predictive Evaluation continued 6. Modelling: The keystroke level model continued The keystroke level model consists of physical motor operators: K (keystroke), P (pointing), H (homing), D (drawing). It also consists of a mental operator M (the user) and a response operator R (the system).

17. Evaluation of User Interface Design 4. Predictive Evaluation continued 6. Modelling: The keystroke level model continued The keystroke level model is quite old and only deals with command line interfaces, so dragging and clicking from today‘s graphical user interfaces were not considered in this model.

18. Evaluation of User Interface Design 4. Predictive Evaluation continued 6. Modelling: The keystroke level model continued Execution time in the keystroke level model is simply the sum of the time for each operator: T=T(K)+T(P)+T(D)+T(M)+T(H)+(R).

19. Evaluation of User Interface Design 4. Predictive Evaluation continued 6. Modelling: The keystroke level model continued There is the assumption that the task starts with a homing action when the user places his/her hand on the mouse.

20. Evaluation of User Interface Design Some final remarks about Evaluation: It is important to carry out evaluation. Not even the best organised and planned design implementation can replace evaluation. Before doing an evaluation we must state which question our evaluation is intended to answer or which hypothesis it is about to test.

21. Evaluation of User Interface Design Some final remarks about Evaluation: It is generally considered a good idea to run a pilot study first. This is a small study to test the procedures that will be used in the larger evaluation study. The benefits of carrying out a pilot study are that the main evaluation study can be planned better afterwards (e.g. it gives us the chance to practise the evaluation). End of lecture