Instructor: Vincent Duffy, Ph.D. Associate Professor of IE Lecture 7 – Displays & Controls Tues. Feb. 6, 2007 IE 486 Work Analysis & Design II

IE 486 Lecture 7 - QOTD QOTD 1: How can you categorize the 13 principles of display design? QOTD 2: What are some perceptual principles? QOTD 3: What is an example of a principle related to mental models?

Administrative Jackie’s office hours: T 12:30-1:30; Th 11-1pm; GRIS 244 or Clickers- old- register to room –New – automatic –Purchase approx. $20 at bookstore –Clickers – begin use on Friday Exam next Thursday (through lecture 7; incl. labs 1 & 2) –Exam in lecture period (closed book, closed notes) In lab on Friday –Exam review in lab –Also 2 readings/presentations on Friday – as part of lifelong learning lab

Question from student Student wrote: > Hi Prof., > > I have a question for you. Do I have to read all parts of every chapter as mentioned in syllabus? Or only the parts that are pertinent to the materials discussed in class? > > Please advise. Thank you. > > Dear Student, Thanks for your question. I am suggesting the reading as a guide for how to gain additional information about the lecture notes. If the chapter helps you to gain additional insight, then you should read it. It is really up to you. As I mentioned in class, sometimes reading the chapter in advance of the lecture can actually help the lecture make more sense when you hear it. (Other students may gain more from reading it after lecture.) Different people learn the material with different styles. During the exam review, I will probably highlight a few of the figures - where some figures (from the text) could be helpful in giving additional insight. Hope that helps. Regards, Vince Duffy

Displays: 13 principles of design of displays Separated into four areas –Perceptual principles –Mental model principles –Attention principles –Memory principles A brief summary is included in the following… (see also ch. 8; displays – p , builds on discussion of cognition from ch. 6)

Figure 8.1. Key components of display design This considers System/information – Display – Senses – Understanding (see below)

13 principles of design of displays QOTD 1: How can you categorize the 13 principles of display design? (see also ch. 8; displays – p , builds on discussion of cognition from ch. 6)

13 principles of design of displays QOTD 1: How can you categorize the 13 principles of display design? Broken into four areas –Perceptual principles –Mental model principles –Memory principles –Attention principles (see also ch. 8; displays – p , builds on discussion of cognition from ch. 6)

Displays-Perceptual Principles QOTD 2: What are some perceptual principles? Top down processing –People will perceive and interpret signals based on what they expect A checklist – takes advantage of expectancy If those things on the list are ‘on’, then proceed. Redundancy gain –Same message is expressed more than once Eg. The traffic light Takes advantage of position and color/hue

Displays-Mental model principles QOTD 3: What is an example of a principle related to mental models? Eg. Principle of pictorial realism –A display should look like the variable it represents –For instance, if we think of temperature as having a high and low value, Then we should consider having the thermometer ‘vertically’ oriented.

Displays-Mental model principles Eg. Principle of pictorial realism –A display should look like the variable it represents –For instance, if we think of temperature as having a high and low value, Then we should consider having the thermometer ‘vertically’ oriented.

Displays - Memory principles We (humans) are not so good at predicting –Predictive aiding or predictive displays can be a help. In providing situation awareness During operations we will consider current and future conditions –and the rules that may lead the current state to the future state. Our mental resources may be consumed with other tasks –Rather than predict, we may just react. Typically proactive behavior is more effective than reactive behavior –A good design will try to minimize the cognitive (or memory based task) and replace it with a perceptual one.

Displays - Memory principles For example, we may need to know the distance between aircraft, –we could show in graphical form of the expected path, and illustrate trajectory (prediction) to show (help us perceive) when we may become ‘too close’ without further adjustment/manipulation (see old fig. 8.4 a. scanned)

Displays - Memory principles For example, we may need to know the distance between aircraft, –we could show in graphical form of the expected path, and illustrate trajectory (prediction) to show (help us perceive) when we may become ‘too close’ without further adjustment/manipulation (see old fig. 8.4 a. scanned)

Displays- Principles based on attention In good designs, –frequently accessed items in software should be in a location such that the cost of traveling between them is small. Minimize information access cost Typically there is a cost in time or effort to move attention from one display to another. Proximity of displays close (or similar colored) and considers which may be needed together at critical times. Consider also ‘multiple resources’. –May present auditory and visual information concurrently rather than ‘all auditory’ or ‘all visual’

Controls Origins of human factors (Fitts, 50s & 60s) –Operator response Depends on the following design attributes –Decision complexity –Expectancy –Compatibility –Speed-accuracy tradeoff –Feedback

Controls- Decision complexity Hick-Hyman Law –reaction time can be predicted as a function of decision complexity According to the formula RT= a+bLog2N –Where N is the number of possible stimulus response alternatives

Controls- Expectancy & Compatibility Expectancy discussed earlier –In terms of checklists Compatibility – discussed earlier in terms of realism of display Simple compatibility example Don’t have operator move a lever to the left if the display indicator will show it moving to the right

Controls- Speed-accuracy tradeoff In preceding concepts, assume longer response will also make more errors –(eg. More complex decisions, unexpected actions, or incompatible responses.) However, if those are constant, we would assume that the faster an operator proceeds through an exercise (given constant level of expertise-learning) –Then they make more errors This is a speed-accuracy tradeoff

Controls- Positioning control Fitts’ Law –MT=a+blog 2 (2A/W) Assume movements take time –Prediction of the time can be done in relation to the ‘index of difficulty’ of the movement A=amplitude of the movement W=width (desired precision) Movement time is linearly related to log of ‘index of difficulty’ (2A/W)

Task Analysis Methods –Industrial Engineering TimeMethods –Physiological –Psychological Structured Questionnaire Unstructured Questionnaire Flow Charts

IE extending into origins of HFE: Fitts’ Law (1954) Example: Objective: To minimize the movement time in screen design. MT = a + b log 2 (2A/W) –MT is movement time –A is the distance to travel to the target –W is the width of the target in menu Comes from positioning ‘Controls’ devices ch.9 (p )

Fitts’ Law Objective: To minimize the movement time in screen design. MT = a + b log 2 (2A/W) –MT is movement time –A is the amplitude (of the distance to traveled to the target) –W is the width of the target in menu –Constants a and b can be derived from empirical studies log 2 (2A/W) commonly called ID (Index of difficulty) For instance, –If A =4 & W=1, then ID=3 –If A=8 & W=1, then ID=4 –If A=4, & W=1/2, then ID=4

Related to Information theory; translates to: ID(bits) = log 2 (2A/W) ID: Index of Movement Difficulty A: The amplitude or distance an operator must move to complete a movement (in.) W: Width of the target (in.) Total Time = [K p ]+[C d ×H t ]+[K m +C m ×log 2 (2A/W)] K p =Perceptual Delays (assumed to be 0.25 sec.) C d =Time needed to process one bit of information (assumed to be 0.22sec/bit) H t =Transmitted Information in bits (log 2 N) N = the number of items in the menu K m =Delay constant (for hand movements, usually 0.177sec.) C m =Measure of information handling ability (usually 0.1sec/bit)

Task and Job Analysis Choice-Entry Time as a Function of Task Parameters N, A, and W

Related to Information theory; translates to: Total Time = [K p ]+[C d ×H t ]+[K m +C m ×log 2 (2A/W)] K p =Perceptual Delays (assumed to be 0.25 sec.) C d =Time needed to process one bit of information (assumed to be 0.22sec/bit) H t =Transmitted Information in bits (log 2 N) N = the number of items in the menu K m =Delay constant (for hand movements, usually 0.177sec.) C m =Measure of information handling ability (usually 0.1sec/bit) Numerical Example for Line 1 on the table of entry time: Total Time = [K p ]+[C d ×H t ]+[K m +C m ×log 2 (2A/W)] =0.25 sec.+[0.22sec/bit×2]+[0.177sec.+0.2sec/bit×6.6bits =0.25 sec.+[0.22sec/bit×2]+[0.177sec.+0.2sec/bit×6.6bits = 2.19 sec. = 2.19 sec. where ID(bits) = log 2 (2A/W)=log 2 (2×12/0.25)=6.6 where ID(bits) = log 2 (2A/W)=log 2 (2×12/0.25)=6.6 C m depends on how many bits the task consists of. Since the entire task has 2 bits (see table), C m is taken as 0.2s here (from 2 bits*0.1s/bit).