Task Analysis in User-Centered Design (cont.)

Marti Hearst (UCB SIMS)SIMS 213, UI Design &

DevelopmentFebruary 4, 1999

Last Time

Why/What is Task Analysis? Creating user-based task scenarios Gathering the data for the

scenarios:– Who are the users?– What are their tasks? – How frequently do they perform these

tasks?

Today

Gathering contextual information:– How are the tasks learned?– Where are they performed? – What are the properties of the data?– What other tools?– How do users communicate?– What are the time constraints?– What can go wrong?

What makes a good scenario

Unresolved Questions from Last Time

Four questions:– Do people really do this user-centered design stuff in

the real world?– If so, do people use exactly this methodology?– How do you combine results for different users into one

interface?– Do you use these techniques before or after selecting

users? Some additional readings help answer these:

– Holtzblatt, Beyer, Cleary, Ims in ACM Interactions Magazine, Jan/Feb 1999. (online next month)

– Holtzblatt & Meyer, Communications of the ACM 36(10), 1993. (hyperlinked from our web site)

– see http://www.acm.org/dl

Task-Centered Design Create Scenarios

– Find out» who users are» what tasks they need to perform

– Create scenarios representing actual use Design

– Decide which users and tasks to support– Design based on these

Evaluation– Test interface by “walking through” it using

scenarios– Do this before implementation

use the followingquestions

Slide adapted from Ben Shneiderman

Scenario Development Characterize what happens when

users perform typical tasks– First, collect info on who, what, when

» interviews, ethnographic studies, surveys

– Then, combine into scenarios Tools for combining:

– table of user communities vs tasks– table of task sequences– flowchart or transition diagram– videotape depicting scenario

Slide adapted from James Landay's

How are Tasks Learned?

What does the user need to know? Do they need training?

– general knowledge/skills– special instruction/training– academic

How are Tasks Learned? (E-commerce) Read tutorial on using the system?

– Is anyone willing to do this? Tutorial on the product line?

– Could be useful Follow simple sequence of steps?

– Does this limit users’ options too much– What about a Shopping Wizard (like installation wizards)

Transfer knowledge from real online shopping?– shopping carts– sales

Transfer knowledge from other online shopping?– virtual shopping cart– secure servers– review purchase before buying -- what if a new site does not

allow this?

Slide adapted from James Landay's

Where is the Task Performed?

Office, home, laboratory, point of sale?

Users under stress?

Confidentiality required?

Effects of environment on users:– Lighting?– Noise?– Hands full?– Standing/sitting?

Where is the Task Performed(E-commerce)

At home– may have slow internet link

At a mall– noisy, people waiting in line– others looking over your shoulder

In the nursery school office– interruptions

Slide adapted from James Landay's

What is the Relationship between Users and Data?

Personal Data– always accessed at the same machine?– Cookies?

Common Data– used concurrently?– passed sequentially between users?– other data sources needed?

Access– Remote access required?– Access to data restricted?

Data Characteristics– reliability– quality– volume (how much?)

Data Relationships (E-Commerce)

Personal data– about credit, past purchases

Common data– info on the web pages– what is known about the vender?– (purchaser must supply a valid address to get

something delivered) Access?

– remote access needed, access to confidential purchasing information needed (until e-cash)

Data Characteristics?– hard to confirm currently

Slide adapted from James Landay's

What Other Tools Does the User Have?

How user works with collection of tools – Example: Electronic Scientific

Publishing»how is the content collected?»what media/forms are used and how are

they handled?»how is the information analyzed?»how is it converted for presentation?

Slide adapted from James Landay's

How do Users Communicate with Each Other?

Who communicates with whom?– follow lines of the organization– against it?– outside an organization?

Why?

How do users communicate with each other? (E-commerce)

Why?– Price comparisons– Recommendations– Warnings

How?– Email?– Hotlists?– Phone calls?– Print-outs?

Slide adapted from James Landay's

What are the Time Constraints on the Task?

What functions will users be in a hurry for?

Which can wait? Is there a timing relationship

between tasks? Are their other kinds of

dependencies between tasks?

Slide adapted from James Landay's

What are the Time Constraints on the Task?

Hurry? Wait? Is there a timing relationship between

tasks?– between clicking on order and viewing the order– between ordering and receiving the product

Are their other kinds of dependencies between tasks?– Run out of stock– New government regulations

Slide adapted from James Landay's

What Happens When Things Go Wrong?

This is one of the most important considerations– How do people deal with

» task-related errors?»practical difficulties?»catastrophies?

– Is there a backup strategy? Scenario walk-throughs can help

identify these Other evaluation methods too.

Which Tasks? (E-Commerce) A scenario

– Isabelle is a mother of two. She browses the product descriptions to try to find an educational toy appropriate for a 7 year old. She finds a chemistry set and “places” it in her virtual shopping cart. She continues browsing the site, adding a Scrabble game for her 10-year-old, and a book for her 7-year-old to the cart. When she goes to “check out” she suddenly remembers she doesn’t need the Scrabble set (they are getting a hand-me-down) and wants to check what the better business bureau says about the safety of the chemistry set before making the purchase. (It turns out ok.) Then she decides she also wants to send the same book to a friend for her daughter, gift-wrapped. She makes the purchases using a credit card.

Slide adapted from Saul Greenberg's

Good Scenarios Say what the user wants to do but

not how they will do it– no assumptions about the interface– can be used to compare different

design alternatives in a fair way Are very specific

– Says exactly what the user wants to do

– Specify input, output

Slide adapted from Saul Greenberg's

Good Scenarios

Some should describe a complete job– Not just a list of things to do– Forces designer to consider how things

will link together– Information flow

»where does information come from?»where does it go?»what has to happen next?

Slide adapted from Saul Greenberg's

Good Scenarios

Say who the users are– design can differ depending on users,

their situation, the expectations of learning, etc

– can make up names for different composite users

Slide adapted from Saul Greenberg's

Good Scenarios

Are evaluated– Circulate descriptions to potential

users»Rewrite if needed»Ask users for

corrections omissions clarifications suggestions

– Do walk-throughs

Slide adapted from James Landay's

Using Task Examples in Design

Users are not always right– cannot anticipate new technology

The job is to build systems users will want– Not systems they say they want– The task analysis should help

determine what they really want

Slide adapted from James Landay's

Using Task Examples in Design Write up a description of the tasks

– formally or informally– show it to users and the other design team

members Roughly sketch an interface design

– major screens and functions (not too detailed)– hand-sketched, informal

Produce scenarios that apply the interface to each task– what user has to do and what they will see– step-by-step performance of task

Formalisms The book introduces several

– HTA: Hierarchical Task Analysis (Ch 7)» Useful for hierarchically decomposing complex

processes» Allows for fixed or discresionary ordering of

actions, optional actions, waiting for events, cycles, simultaneity.

» But, hard to do well, can get complex quickly

– Other useful ones: (Ch 8.1-8.3)»State transition networks»Flow charts

each have strengths and weaknesses

Formalisms Better to use sketchy, informal

descriptions initially– invite modification– don’t spend lots of time perfecting

something that isn’t ready to be analyzed in detail

Useful for later in the design process– identify commonalities among possible

paths – identify complexities in the design– help inform the software designers

Slide adapted from Saul Greenberg's

Walk-Throughs Good for development and debugging Process:

– Select one of the task scenarios– For each user action/step in the scenario

» can you build a believable story about why the user will take that step with this interface?

» can you rely on user’s expected knowledge and training?

– If not,» you found a problem!» now that it is identified, assume it is repaired » go to next step in the scenario

Next Week

How People Work– The perceptual system– Basic cognitive properties