Instructor: Vincent Duffy, Ph.D.Instructor: Vincent Duffy, Ph.D.

Associate Professor of IEAssociate Professor of IE

Lecture 7 – Displays & Controls Lecture 7 – Displays & Controls

Tues. Feb. 6, 2007Tues. Feb. 6, 2007

IE 486 Work Analysis & Design IIIE 486 Work Analysis & Design II

IE 486 Lecture 7 - QOTDIE 486 Lecture 7 - QOTD

QOTD 1: How can you categorize the 13 QOTD 1: How can you categorize the 13 principles of display design? principles of display design?

QOTD 2: What are some perceptual QOTD 2: What are some perceptual principles?principles?

QOTD 3: What is an example of a QOTD 3: What is an example of a principle related to mental models?principle related to mental models?

AdministrativeAdministrative

Jackie’s office hours: T 12:30-1:30; Th 11-1pm; GRIS Jackie’s office hours: T 12:30-1:30; Th 11-1pm; GRIS 244 or email244 or emailClickers- old- register to roomClickers- old- register to room– New – automatic New – automatic – Purchase approx. $20 at bookstorePurchase approx. $20 at bookstore– Clickers – begin use on FridayClickers – begin use on Friday

Exam next Thursday (through lecture 7; incl. labs 1 & 2)Exam next Thursday (through lecture 7; incl. labs 1 & 2)– Exam in lecture period (closed book, closed notes)Exam in lecture period (closed book, closed notes)

In lab on FridayIn lab on Friday– Exam review in labExam review in lab– Also 2 readings/presentations on Friday – as part of lifelong Also 2 readings/presentations on Friday – as part of lifelong

learning lablearning lab

Question from studentQuestion from student

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

Displays: 13 principles of design of displaysDisplays: 13 principles of design of displays

Separated into four areasSeparated into four areas– Perceptual principlesPerceptual principles– Mental model principlesMental model principles– Attention principlesAttention principles– Memory principlesMemory principles

A brief summary is included in the A brief summary is included in the following…following…

((see alsosee also ch. 8; displays – p.186-193, builds on discussion ch. 8; displays – p.186-193, builds on discussion of cognition from ch. 6)of cognition from ch. 6)

Figure 8.1. Key components of display designFigure 8.1. Key components of display design

This considers System/information – Display – Senses – Understanding (see below)This considers System/information – Display – Senses – Understanding (see below)

13 principles of design of displays13 principles of design of displays

QOTD 1: How can you categorize the 13 QOTD 1: How can you categorize the 13 principles of display design?principles of display design?

(see also ch. 8; displays – p.186-193, builds on discussion of cognition (see also ch. 8; displays – p.186-193, builds on discussion of cognition from ch. 6)from ch. 6)

13 principles of design of displays13 principles of design of displays

QOTD 1: How can you categorize the 13 QOTD 1: How can you categorize the 13 principles of display design?principles of display design?

Broken into four areasBroken into four areas– Perceptual principlesPerceptual principles– Mental model principlesMental model principles– Memory principles Memory principles – Attention principlesAttention principles

(see also ch. 8; displays – p.186-193, builds on discussion of cognition (see also ch. 8; displays – p.186-193, builds on discussion of cognition from ch. 6)from ch. 6)

Displays-Perceptual PrinciplesDisplays-Perceptual Principles

QOTD 2: What are some perceptual principles?QOTD 2: What are some perceptual principles?

Top down processingTop down processing– People will People will perceive and interpretperceive and interpret signals based on signals based on

what they what they expectexpectA checklist – takes advantage of expectancyA checklist – takes advantage of expectancy

If those things on the list are ‘on’, then proceed.If those things on the list are ‘on’, then proceed.

Redundancy gainRedundancy gain– Same message is expressed more than onceSame message is expressed more than once

Eg. The traffic lightEg. The traffic light

Takes advantage of position and color/hueTakes advantage of position and color/hue

Displays-Mental model principlesDisplays-Mental model principles

QOTD 3: What is an example of a principle QOTD 3: What is an example of a principle related to mental models?related to mental models?

Eg. Principle of pictorial realismEg. Principle of pictorial realism– A display should look like the variable it A display should look like the variable it

representsrepresents– For instance, if we think of For instance, if we think of temperaturetemperature as as

having a having a highhigh and and lowlow value, value, Then we should consider having the thermometer Then we should consider having the thermometer ‘vertically’ oriented. ‘vertically’ oriented.

Displays-Mental model principlesDisplays-Mental model principles

Eg. Principle of pictorial realismEg. Principle of pictorial realism– A display should look like the variable it representsA display should look like the variable it represents– For instance, if we think of For instance, if we think of temperaturetemperature as having a as having a highhigh and and lowlow value, value,

Then we should consider having the thermometer ‘vertically’ oriented. Then we should consider having the thermometer ‘vertically’ oriented.

Displays - Memory principlesDisplays - Memory principles

We (humans) are We (humans) are notnot so good at predicting so good at predicting– Predictive aiding or predictive displays can be a help.Predictive aiding or predictive displays can be a help.

In providing situation awarenessIn providing situation awareness

During operations we will consider During operations we will consider current and current and future conditions future conditions – and the rules that may lead the current state to the future and the rules that may lead the current state to the future

state.state.

Our mental Our mental resourcesresources may be may be consumedconsumed with other with other taskstasks– Rather than predict, we may just react.Rather than predict, we may just react.

Typically proactive behavior is more effective than Typically proactive behavior is more effective than reactive behaviorreactive behavior– A good design will try to A good design will try to minimizeminimize the cognitive (or the cognitive (or

memory based task) and memory based task) and replace it withreplace it with a perceptual one. a perceptual one.

Displays - Memory principlesDisplays - Memory principles

For example, we may need to know the For example, we may need to know the distance between aircraft, distance between aircraft, – we could show in graphical form of the we could show in graphical form of the

expected path, expected path, and illustrate trajectory (prediction) to show (help and illustrate trajectory (prediction) to show (help us perceive) when we may become ‘too close’ us perceive) when we may become ‘too close’ without further adjustment/manipulationwithout further adjustment/manipulation

(see old fig. 8.4 a. scanned)(see old fig. 8.4 a. scanned)

Displays - Memory principlesDisplays - Memory principles

For example, we may need to know the distance between aircraft, For example, we may need to know the distance between aircraft, – we could show in graphical form of the expected path, we could show in graphical form of the expected path,

and illustrate trajectory (prediction) to show (help us perceive) when we may and illustrate trajectory (prediction) to show (help us perceive) when we may become ‘too close’ without further adjustment/manipulation become ‘too close’ without further adjustment/manipulation

(see old fig. 8.4 a. scanned)(see old fig. 8.4 a. scanned)

Displays- Principles based on attentionDisplays- Principles based on attention

In good designs,In good designs,– frequently accessed items in software should be in a frequently accessed items in software should be in a

location such that the cost of traveling between them location such that the cost of traveling between them is small.is small.

Minimize information access costMinimize information access costTypically there is a Typically there is a cost in timecost in time or effort to move attention or effort to move attention from one display to another.from one display to another.

Proximity of displays close (or similar colored) and considers Proximity of displays close (or similar colored) and considers which may be needed together at critical times.which may be needed together at critical times.

Consider also ‘multiple resources’.Consider also ‘multiple resources’.– May present auditory and visual information May present auditory and visual information

concurrently rather than ‘all auditory’ or ‘all visual’concurrently rather than ‘all auditory’ or ‘all visual’

ControlsControls

Origins of human factors (Fitts, 50s & 60s)Origins of human factors (Fitts, 50s & 60s)– Operator responseOperator response

Depends on the following design attributesDepends on the following design attributes

– Decision complexityDecision complexity– ExpectancyExpectancy– CompatibilityCompatibility– Speed-accuracy tradeoffSpeed-accuracy tradeoff– FeedbackFeedback

Controls- Decision complexityControls- Decision complexity

Hick-Hyman Law Hick-Hyman Law – reaction time can be predicted as a function of reaction time can be predicted as a function of

decision complexitydecision complexityAccording to the formula RT= a+bLog2NAccording to the formula RT= a+bLog2N

– Where N is the number of possible stimulus response Where N is the number of possible stimulus response alternativesalternatives

Controls- Expectancy & Controls- Expectancy & CompatibilityCompatibility

Expectancy discussed earlierExpectancy discussed earlier– In terms of checklists In terms of checklists

Compatibility – discussed earlier in terms Compatibility – discussed earlier in terms of realism of display of realism of display

Simple compatibility exampleSimple compatibility exampleDon’t have operator move a lever to the left Don’t have operator move a lever to the left

if the display indicator will show it moving to the if the display indicator will show it moving to the rightright

Controls- Speed-accuracy Controls- Speed-accuracy tradeofftradeoff

In preceding concepts, assume longer In preceding concepts, assume longer response will also make more errors response will also make more errors – (eg . More complex decisions, unexpected actions, (eg . More complex decisions, unexpected actions,

or incompatible responses.)or incompatible responses.)

However, if those are constant, we would However, if those are constant, we would assume that the faster an operator proceeds assume that the faster an operator proceeds through an exercise (given constant level of through an exercise (given constant level of expertise-learning)expertise-learning)– Then they make more errorsThen they make more errors

This is a speed-accuracy tradeoffThis is a speed-accuracy tradeoff

Controls- Positioning controlControls- Positioning control

Fitts’ LawFitts’ Law– MT=a+blogMT=a+blog22(2A/W)(2A/W)

Assume movements take timeAssume movements take time– Prediction of the time can be done in relation to Prediction of the time can be done in relation to

the ‘index of difficulty’ of the movementthe ‘index of difficulty’ of the movement

A=amplitude of the movementA=amplitude of the movement

W=width (desired precision)W=width (desired precision)

Movement time is linearly related to log of Movement time is linearly related to log of ‘index of difficulty’ (2A/W)‘index of difficulty’ (2A/W)

Task AnalysisTask Analysis

MethodsMethods– Industrial EngineeringIndustrial Engineering

TimeTime

MethodsMethods

– PhysiologicalPhysiological– PsychologicalPsychological

Structured QuestionnaireStructured Questionnaire

Unstructured QuestionnaireUnstructured Questionnaire

Flow ChartsFlow Charts

IE extending into origins of HFE: IE extending into origins of HFE: Fitts’ Law Fitts’ Law (1954)(1954)

Example: Example: Objective: To minimize the movement time Objective: To minimize the movement time

in screen design.in screen design.

MT = a + b logMT = a + b log22(2A/W)(2A/W)– MT is movement timeMT is movement time– A is the distance to travel to the targetA is the distance to travel to the target– W is the width of the target in menuW is the width of the target in menu

Comes from positioning ‘Controls’ devices ch.9 Comes from positioning ‘Controls’ devices ch.9 (p.223-225)(p.223-225)

Fitts’ LawFitts’ LawObjective: To minimize the movement time in Objective: To minimize the movement time in

screen design.screen design.

MT = a + b logMT = a + b log22(2A/W)(2A/W)– MT is movement timeMT is movement time– A is the amplitude (of the distance to traveled to the target)A is the amplitude (of the distance to traveled to the target)– W is the width of the target in menuW is the width of the target in menu– Constants a and b can be derived from empirical studiesConstants a and b can be derived from empirical studies

loglog22(2A/W) (2A/W) commonly called ID (Index of difficulty)commonly called ID (Index of difficulty)

For instance, For instance, – If A =4 & W=1, then ID=3If A =4 & W=1, then ID=3– If A=8 & W=1, then ID=4If A=8 & W=1, then ID=4– If A=4, & W=1/2, then ID=4If A=4, & W=1/2, then ID=4

Related to Information theory; Related to Information theory; translates to:translates to:

ID(bits) = logID(bits) = log22(2A/W)(2A/W)ID: Index of Movement DifficultyID: Index of Movement DifficultyA: The amplitude or distance an operator must move to A: The amplitude or distance an operator must move to complete a movement (in.)complete a movement (in.)W: Width of the target (in.)W: Width of the target (in.)

Total Time = [KTotal Time = [Kpp]+[C]+[Cdd×H×Htt]+[K]+[Kmm+C+Cmm×log×log22(2A/W)](2A/W)]KKpp=Perceptual Delays (assumed to be 0.25 sec.)=Perceptual Delays (assumed to be 0.25 sec.)CCdd=Time needed to process one bit of information =Time needed to process one bit of information (assumed to be 0.22sec/bit)(assumed to be 0.22sec/bit)HHtt=Transmitted Information in bits (log=Transmitted Information in bits (log22N)N)N = the number of items in the menuN = the number of items in the menuKKmm=Delay constant (for hand movements, usually =Delay constant (for hand movements, usually 0.177sec.)0.177sec.)CCmm=Measure of information handling ability (usually =Measure of information handling ability (usually 0.1sec/bit)0.1sec/bit)

Task and Job AnalysisTask and Job Analysis

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

Related to Information theory; Related to Information theory; translates to:translates to:

Total Time = [KTotal Time = [Kpp]+[C]+[Cdd×H×Htt]+[K]+[Kmm+C+Cmm×log×log22(2A/W)](2A/W)]KKpp=Perceptual Delays (assumed to be 0.25 sec.)=Perceptual Delays (assumed to be 0.25 sec.)CCdd=Time needed to process one bit of information (assumed to be =Time needed to process one bit of information (assumed to be 0.22sec/bit)0.22sec/bit)HHtt=Transmitted Information in bits (log=Transmitted Information in bits (log22N)N)N = the number of items in the menuN = the number of items in the menuKKmm=Delay constant (for hand movements, usually 0.177sec.)=Delay constant (for hand movements, usually 0.177sec.)CCmm=Measure of information handling ability (usually 0.1sec/bit)=Measure of information handling ability (usually 0.1sec/bit)

Numerical Example for Line 1 on the table of entry time:Numerical Example for Line 1 on the table of entry time:

Total Time = [KTotal Time = [Kpp]+[C]+[Cdd×H×Htt]+[K]+[Kmm+C+Cmm×log×log22(2A/W)](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) = logwhere ID(bits) = log22(2A/W)=log(2A/W)=log22(2(2××12/0.25)=6.612/0.25)=6.6

CCmm depends on how many bits the task consists of. Since the entire task has 2 bits (see depends on how many bits the task consists of. Since the entire task has 2 bits (see table), Ctable), Cmm is taken as 0.2s here (from 2 bits*0.1s/bit). is taken as 0.2s here (from 2 bits*0.1s/bit).