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

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…

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

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.

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

See ‘iterative’ cycle for system development.

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).

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 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 –Action specification – necessary sequence –Interface mechanism

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 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

QOTD. Q1. What is a GOMS model? What is the purpose of a GOMS analysis? See p 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 . 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).

Recall in HCI: GOMS model & GOMS analysis? Goals, Operators, Methods, Selection Rules –Predictive Models of Task Performance See p 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 . –Sub-goal- make blank page to write on –So the subgoals can have equivalent related to the operators –Eg. Choose menu item ‘compose new ’

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 – operator decides (next procedures) whether to listen, respond/speak, or transfer customer –Motor operations – left hand, right hand, eye movements

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).

Recall illustration of benefits of using the GOMS model (NYNEX example). This case was initially described by Gray et al 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 ) –R.S. Bridger, 2003, Introduction to Ergonomics, 2 nd Ed., Taylor and Francis Publishers: UK.

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 )

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.

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

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