Human-Computer InteractionTask Analysis & Design

Alexiei Dingliadingli@stmartins.edu

Task Analysis (1)

• Analysis the process in which humans play a role

• Study of systems in terms of human behaviour• How people use such systems?• What resources they use?• What they need to know to use such systems?

• Involves• Observation• Recording• Usage of that knowledge to build systems which

match user tasks & needs

Task Analysis (2)

• Not only confined to the computer element

• Tries to model all human activities involved

• Used in the initial stages of system design• Clarification of required task• Requirements capture

• Problems which we might encounter? • Which new features?• Which old features?• Innovation?

Task Analysis Techniques• Involve sub-dividing/decomposing tasks into

• Meaningful • Manageable units

• Such techniques include• Hierarchical Task Analysis (HTA)

• Creates hierarchy & sequence of tasks, sub-tasks, etc.

• Knowledge-based Task Analysis (KBTA)• Creates ordered lists of components / tasks

• Systems analytic techniques• Decomposes tasks but the ordering is focused more

on the system

Uses of Task Analysis• Analytical method to determine how people

carry out work practices. It …

• Analyses how existing computer systems support the tasks

• Identify & group user tasks in a structured fashion• Design & implements prototypes• Assist in the redesign of existing interfaces• Help design support & training material• Help in requirement analysis

HTA (Annett & Duncan 1967)

• Most commonly used form of Task Analysis

• Graphical representation

• Decomposition of high level task into constituent subtasks, operations, plans

• Uses structure chart notation  

HTA Notation

Starting the Analysis• Define the area of work

• Break it down into main tasks

• Break down main task into 4-8 subtasks; specify subtasks in terms of objectives

• Draw subtasks as layered plans

Progressing the analysis (1)• Choose level of detail

• Treat each branch consistently• Decide at which level to stop

• “click mouse” v. “delete block of text”

• Choose depth-first, breadth-first, or combo

• Use hierarchical numbering convention• 1, 2, 3, then 1.1, 1.2, 1.3 and so on ... 

Progressing the analysis (2)

• Outline Plan for each task• Describe how tasks are carried out (at the next

level)

• Number steps in the sequence they should be followed. 

Progressing the analysis (3)

• Types of plans include• Fixed Sequence• Optional tasks• Waiting for events• Cycles• Time sharing (simultaneously)• Discretionary (free will)• Mixtures 

Finalising the analysis• Check

• Consistency • Accuracy• Completeness

• Check numbering is consistent with decomposition

• Check the accuracy of the notation

HTA Example 1Hierarchy description ... How to clean the house?• 0. in order to clean the house • 1. get the vacuum cleaner out • 2. fix the appropriate attachment • 3. clean the rooms • 3.1. clean the hall • 3.2. clean the living rooms • 3.3. clean the bedrooms • 4. empty the dust bag • 5. put vacuum cleaner and attachments away  

HTA Example 1 Plans• ... and plans

• Plan 0: do 1 - 2 - 3 - 5 in that order. when the dust bag gets full do 4.

• Plan 3: do any of 3.1, 3.2 or 3.3 in any order depending on which rooms need cleaning  

HTA Example 2 Diagram

HTA Example 2 Refinement

HTA Example 3

• How would you go about preparing a Microsoft word document?

HTA Example 3

HTA Example 3 Refined

HTA Outcome• Manuals

• HTA provides structured information• Helps users transfer between one system & another

• Requirements Capture• Provide information on

• Existing operations, • objects & • ways of performing tasks

• Interface design• Top level can be used as menus headers• Task sequence can be used for user-system

dialogues

Exercise 1

• How would you go about sending an MMS complete with text and image?

Knowledge-Based Task Analysis

• Creates taxonomies of a task

• Similar to generic hierarchies

• Aim is to classify • Knowledge needed to complete a task

• Rather than• Classify the procedures

• KBTA does not only show sequence but also• Links between elements• It provides a fuller model

KBTA Example 1• Classifying motor vehicle controls objects• Motor vehicle controls

• steering steering wheel, indicators• engine/speed

• direct starter, accelerator, foot brake

• gears clutch, gear lever

• lights• external headlights, hazards• internal roof light

• wash/wipe• wipers front, rear• washers front, rear

System Analysis Techniques (1)• Data Flow Diagram (DFD)

• Describe flow of information between processes & stores

• Adaptable to task analysis

System Analysis Techniques (2)• DFD Example – Book Ordering System

System Analysis Techniques (3)• Entity-Relational

Models• Associated with

DB design & OO analysis

• Similar to KBTA since it describes objects & actions

• But ERM explicitly defines relationships

System Analysis Techniques (4)

Requirements Gathering • From several sources

• Existing documentation • +cheap, -does not offer direct information

• Direct observation• Informally watching, observing, monitoring, using specialised

recording equipment, walkthroughs

• Interviewing• Elicit experts, to uncover task decomposition

• Questionnaire• Answers to specific questions

• Quantitative survey data• Qualitative survey data

• Group discussions

• Subjective data

Data Analysis – Card Sorting (1)• Technique for exploring how people group

items, so that you can develop structures that maximize the probability of users being able to find items. • Is easy and cheap to conduct • Enables you to understand how 'real people' are

likely to group items • Identifies items that are likely to be difficult to

categorize and find • Identifies terminology that is likely to be

misunderstood.

Data Analysis – Card Sorting (2)• Group the following elements together in 4 categories

and give each group a title:

• Films & Movies• Diving• Live Music• Hotel• Etiquette• Beaches• Architectural Sites• Night Clubs• Historical Monuments

Data Analysis – Kelly Grids (1)• Ways of getting at the conceptual structure of the

problem space• Identifying some 'elements' in the application

• These might be real things or concepts, but should be organized into coherent sets

• For example, the set {Porsche, Jaguar, Rolls Royce, Mini, Driver} has an obvious odd man out: Driver

• Elicitate new classes by• asking for the opposites of all elements and concepts• laddering to extract generalizations• elicitation by triads extract specializations

• user is asked to take any three elements and specify a concept that applies to two of them but not to the third

• For example, with {Porsche, Jaguar, Mini}, top speed might emerge as an important concept

Data Analysis – Kelly Grids (2)

Other Data Analysis Techniques• Noun-verb method

• Noun tasks-associated object• Verb actions

• Rating Scales• A scale based on descriptive words or phrases that

indicate performance levels• Qualities of a performance are described (e.g.,

advanced, intermediate, novice) in order to designate a level of achievement

John BiscuitEats

Task Analysis + Interface Design

• Detailed TA can be mapped onto functions of a system• Menus• Selections• Sequences• Etc.

• Should be considered as an aid to design• It is an iterative process• User Oriented

• It does not try to understand the user but• Observes behaviour + actions

Conclusion

• TA is an Iterative process which • identifies new data• Confirms existing data• Rejects false data

• Necessary to understand tasks which in turn is necessary for the design of the system

• It highlights the importance of the user

Exercise 2

• Produce a high-level hierarchal task analysis showing how you would find information on a website. Assume the site has a search facility as well as normal links.

Exercise 3

• Consider the activity to make a telephone call. Record the actions in an HTA diagram. Start off simply assuming you know the number to dial.

Exercise 3

• Consider the activity to make a telephone call. Record the actions in an HTA diagram. Start off simply assuming you know the number to dial.

• What if you had to find the number in an address book?

Exercise 3

• Consider the activity to make a telephone call. Record the actions in an HTA diagram. Start off simply assuming you know the number to dial.

• What if you had to find the number in an address book?

• What if the number was engaged?

Useful Links (1)

• http://www.usabilitynet.org/tools/methods.htm

Useful Links (2)• http://www.enquirewithin.co.nz/BUS_APP/

business.htm

Suggested readings for next week• Chapter 6 of Dix et al.