Instructor: Vincent Duffy, Ph.D. Associate Professor of IE

1. IE 486 Work Analysis & Design II Instructor: Vincent Duffy, Ph.D. Associate Professor of IE Lecture 8 – Human-Computer Interaction Thurs. Feb. 8, 2007

2. IE 486 Lecture 8 - QOTD • Q1. What is a GOMS model? What is the purpose of a GOMS analysis? • Q2. The case study illustrates which of the following? • Q3. In a text editing exercise, it is believed that a user decides to use the mouse to move the cursor if the cursor is more than 2 lines from where they will edit the text, but uses the arrow keys otherwise. In a GOMS model, this represents…

3. Usability/HCI Overview • ‘Iterative’ cycle for system development. • Criteria for designing usable software • Norman’s ‘Seven stages of action model’ in relation to goals and actual implemented system • Briefly consider Norman’s ‘Seven stages of action model’ in relation to goals and actual implemented system • GOMS model. What is it; what is the purpose of a GOMS analysis? • Review illustration of benefits • Number of users in evaluation – thinking aloud test

4. Real life example where good/bad computer interface design can be a life or death matter • Consider the example of Ray Cox at the East Texas Cancer Center (p.383 in text). • Technician viewed ‘monitor not plugged in’ as normal; and she’d used the controls dozens of times – it was pretty simple. • However, there was a flaw in the software- when edit function was used very quickly. • Human factors in computers: • hardware design, • software functionality, • interface design.

5. See ‘iterative’ cycle for system development. • See Figure 15.1 (p.387 in text). • Understanding – Design – Evaluation • Other authorities on HCI include: Nielson, Norman, Landauer Understanding Evaluation Design

6. See ‘iterative’ cycle for system development.

7. Criteria for designing usable software (Nielson, 1994) • Learnability • should be easy to learn – to get rapid start in work • Efficiency • So that user has high productivity once learned. • Memorability • Casual user should be able to return after period of time w/out re-learning • Errors • Helpful if system enables low error rate and easy error recovery. • Satisfaction • Pleasant to use; Users should be ‘subjectively’ satisfied. • Priority may be greater or lower based on task characteristics. • see p.59 in new edition of text (Ch.3 on Usability Testing for additional information).

8. Norman’s ‘Seven stages of action model’ in relation to goals and actual implemented system • See figure 15.2 which consists of two bridges and seven steps as outlined on p. 390-391 in text. • User starts with goals, needs to know what to do, and how • To bridge the Gulf of Execution (bridge) • Bridged (by designer) through good controls (ch.9). • User evaluates to determine (bridge) how well goals matched results • Execution Bridge • Intention – send email • Action specification – necessary sequence • Interface mechanism

9. Norman’s ‘Seven stages of action model’ in relation to goals and actual implemented system

10. Briefly consider Norman’s ‘Seven stages of action model’ in relation to goals and actual implemented system • Evaluation Bridge • Interface mechanism/display • Interpretation • Evaluation • Closing the gap between ‘state of system’ and ‘psychological’ model of system state is a challenge for designers

11. QOTD. Q1. What is a GOMS model? What is the purpose of a GOMS analysis? • See p. 392-393 in text as well as p. 45 in Ch.3 – considering Task Data). • Goals, Operators, Methods, Selection Rules– Predictive Models of Task Performance • Eg. Goal – write email. Sub-goals- make blank page to write on – • Methods – sequence of steps – perceptual, cognitive or motor operators • Since several methods can be used to achieve the sub-goals, selection rules are developed/postulated to suggest/identify under what conditions a user will use one method or another. • Eg. Method of ‘print’ could be ‘press printer icon’, mouse click file, print, ok, or choose key sequence (eg. Alt-f-p or Ctrl-p). • Designers/developers may try to determine when what conditions lead to certain methods (to predict performance and learning time).

12. Recall in HCI: GOMS model & GOMS analysis? • Goals, Operators, Methods, Selection Rules • Predictive Models of Task Performance • See p. 392-393 in text as well as p. 45 in Ch.3 – considering Task Data. • In HCI this is a keystroke level model of human-machine interaction • Eg. Goal – write email. • Sub-goal- make blank page to write on • So the subgoals can have equivalent related to the operators • Eg. Choose menu item ‘compose new email’

13. Operators are the methods and procedures that the system makes available • eg. Elementary motor or cognitive acts needed to change the system state – for instance, selecting an item in a menu. • Or the ‘goal’ to ‘edit chapter 15 title’ might consist of subgoals with equivalent operators: ‘open file’, find heading’, ‘delete heading’. • Methods – sequence of steps – • Perceptual – visual or auditory • Cognitive – operatordecides(next procedures) • whether to listen, respond/speak, or transfer customer • Motor operations – left hand, right hand, eye movements

14. Selection Rules - Since several methods can be used to achieve the sub-goals, selection rules are developed/postulated to suggest/identify under what conditions a user will use one method or another. • Eg. Method of ‘print’ could be ‘press printer icon’, mouse click file, print, ok, or choose key sequence (eg. Alt-f-p or Ctrl-p). • Selection rule: choose mouse if line to be edited is +/- 2 lines from cursor current position. • Designers/developers may try to determine when what conditions lead to certain methods (to predict performance and learning time).

15. Recall illustration of benefits of using the GOMS model (NYNEX example). • This case was initially described by Gray et al. 1993 in the journal called Human Computer Interaction. • See p.394 Case study in text. • Gray (1993) et al. used the GOMS model to ‘evaluate’ a new operator workstation for NYNEX (NY Phone Company). • Why there was a 3-4% increase in performance time even though number of keystrokes was reduced? • (consider the keystrokes on the ‘critical path’) • See also 2 sided handout from ‘Intro to Ergonomics’ Bridger(p.459-461) • R.S. Bridger, 2003, Introduction to Ergonomics, 2nd Ed., Taylor and Francis Publishers: UK.

16. Recall illustration of benefits of using the GOMS model (NYNEX example). • See also 2 sided handout on course webpage from ‘Intro to Ergonomics’ Bridger(parts of pages 459-461)

17. Number of users in evaluation • Thinking aloud test –Wickens, see p. 409 in text,refers to T.Landauer;some refer to J.Nielson(1994). • after 5-6 people, the benefit of additional people diminishes. • Suggests developers would be better off making software changes before running additional subjects.

18. IE 486 Lecture 8 - QOTD • Q2. The case study illustrates which of the following? a. the benefits of a task analysis b. the barriers to organizational change c. the information processing model d. all of the above e. none of the above

19. QOTD • Q.3. In a text editing exercise, it is believed that a user decides to use the mouse to move the cursor if the cursor is more than 2 lines from where they will edit the text, but uses the arrow keys otherwise. In a GOMS model, this represents… a. user goals b. methods c. cognitive operators d. all of the above e. none of the above