Chapter 7

Design in the World of Business

Chapter 7

• Design in the marketplace• Featuritis• Timeline for moving from design to product• Incremental vs. radical design• As well as opinions related to

– New media– Augmented humans– Design and the environment

• The future of the Design of Everyday Things

Why, what, where and when to evaluate

Iterative design & evaluation is a continuous process that examines:– Why: to check that users can use the product and that

they like it– What: a conceptual model, early prototypes of a new

system and later, more complete prototypes– Where: in natural and laboratory settings– When: throughout design; finished products can be

evaluated to collect information to inform new productsDesigners need to check that they understand users’

requirements.

Bruce Tognazzini tells you why you need to evaluate

“Iterative design, with its repeating cycle of design and testing, is the only validated methodology in existence that will consistently produce successful results. If you don’t have user-testing as an integral part of your design process you are going to throw buckets of money down the drain.”

See AskTog.com for topical discussions about design and evaluation.

The language of evaluation

• Analytical evaluation• Controlled experiment• Field study• Formative evaluation• Heuristic evaluation• Predictive evaluation

• Summative evaluation• Usability laboratory• User studies• Usability studies• Usability testing• User testing

DECIDE: a framework to guide evaluation

• Determine the goals.• Explore the questions.• Choose the evaluation approach and

methods.• Identify the practical issues.• Decide how to deal with the ethical issues.• Evaluate, analyze, interpret and present the

data.

Determine the goals

• What are the high-level goals of the evaluation?

• Who wants it and why?• The goals influence the approach used for the

study.• Some examples of goals:

- Identify the best metaphor on which to base the design.- Check to ensure that the final interface is consistent.- Investigate how technology affects working practices.- Improve the usability of an existing product.

Explore the questions

• All evaluations need goals & questions to guide them.• E.g., the goal of finding out why many customers prefer

to purchase paper airline tickets rather than e-tickets can be broken down into sub-questions:– What are customers’ attitudes to these new tickets? – Are they concerned about security?– Is the interface for obtaining them poor?

• What questions might you ask about the design of a cell phone?

Choose the evaluation approach & methods

• The evaluation approach influences the methods used, and in turn, how data is collected, analyzed and presented.

• E.g. field studies typically:– Involve observation and interviews.– Do not involve controlled tests in a laboratory.– Produce qualitative data.

Identify practical issues

For example, how to:

• Select users• Stay on budget• Stay on schedule• Find evaluators• Select equipment

Decide about ethical issues

• Develop an informed consent form

• Participants have a right to:- Know the goals of the study;- Know what will happen to the findings;- Privacy of personal information;- Leave when they wish; - Be treated politely.

Institutional Review Board

• Purpose– To protect the rights and welfare of subjects in

evaluations• Process

– IRB reviews evaluation process to ensure it is safe and taking appropriate precautions

• How it relates to CHI evaluations– Most CHI-related evaluations are in the “exempt”

category– Still, there are issues to consider

Evaluate, interpret & present data

• The approach and methods used influence how data is evaluated, interpreted and presented.

• The following need to be considered:- Reliability: can the study be replicated?- Validity: is it measuring what you expected?- Biases: is the process creating biases?- Scope: can the findings be generalized?- Ecological validity: is the environment influencing the findings? - i.e. Hawthorn effect.

Evaluation approaches

• Usability testing• Field studies• Analytical evaluation

• Combining approaches• Opportunistic evaluations

Usability testing

• Involves recording performance of typical users doing typical tasks.

• Controlled environmental settings. • Users are observed and timed.• Data is recorded on video & key presses are logged. • The data is used to calculate performance times, and

to identify & explain errors. • User satisfaction is evaluated using questionnaires &

interviews. • Field observations may be used to provide contextual

understanding.

Experiments & usability testing

• Experiments test hypotheses to discover new knowledge by investigating the relationship between two or more things – i.e., variables.

• Usability testing is applied experimentation. • Developers check that the system is usable by

the intended user population for their tasks.• Experiments may also be done in usability

testing.

Usability testing & research

Usability testing

• Improve products• Few participants• Results inform design• Usually not completely

replicable• Conditions controlled as

much as possible• Procedure planned• Results reported to

developers

Experiments for research

• Discover knowledge• Many participants• Results validated

statistically • Must be replicable• Strongly controlled

conditions• Experimental design• Scientific reported to

scientific community

Usability testing

• Goals & questions focus on how well users perform tasks with the product.

• Comparison of products or prototypes common.• Focus is on time to complete task & number &

type of errors.• Data collected by video & interaction logging.• Testing is central.• User satisfaction questionnaires & interviews

provide data about users’ opinions.

Usability lab with observers watching a user & assistant

Portable equipment for use in the field

Testing conditions

• Usability lab or other controlled space.• Emphasis on:

– selecting representative users;– developing representative tasks.

• 5-10 users typically selected.• Tasks usually last no more than 30 minutes.• The test conditions should be the same for every

participant.• Informed consent form explains procedures and

deals with ethical issues.

Some type of data

· Time to complete a task.· Time to complete a task after a specified. time away

from the product.· Number and type of errors per task.· Number of errors per unit of time.· Number of navigations to online help or manuals.· Number of users making a particular error.· Number of users completing task successfully.

Usability engineering orientation

· Aim is improvement with each version· Current level of performance· Minimum acceptable level of performance· Target level of performance

How many participants is enough for user testing?

• The number is a practical issue.• Depends on:

– schedule for testing;– availability of participants;– cost of running tests.

• Typically 5-10 participants. • Some experts argue that testing should

continue until no new insights are gained.

Experiments

• Predict the relationship between two or more variables.

• Independent variable (e.g. which design) is manipulated by the researcher.

• Dependent variable (e.g. time) depends on the independent variable.

• Typical experimental designs have one or two independent variable.

Experimental designs

• Different participants - single group of participants is allocated randomly to the experimental conditions.

• Same participants - all participants appear in both conditions.

• Matched participants - participants are matched in pairs, e.g., based on expertise, gender, etc.

Different, same, matched participant design

Design Advantages Disadvantages

Different No order effects Many subjects & individual differences a problem

Same Few individuals, no individual differences

Counter-balancing needed because of ordering effects

Matched Same as different participants but individual differences reduced

Cannot be sure of perfect matching on all differences

The Need to Balance

• Why do we balance– For learning effects and fatigue– For interactions among conditions– For unexpected features of tasks

• Latin square study design– Used to balance conditions and ordering effects– Consider balancing use of two systems for two tasks for a

same-participant study

Review of Experimental Statistics

• For normal distributions– T test: for identifying differences between two

populations– Paired T test: for identifying differences between

the same population or a well-matched pair of populations

– ANOVA: for identifying differences between more than two populations

• For predicted distributions– Chi square: to determine if difference from

predicted is meaningful

Field Studies Review

• Field studies are done in natural settings.• The aim is to understand what users do

naturally and how technology impacts them.• Field studies can be used in product design to:

- identify opportunities for new technology;- determine design requirements; - decide how best to introduce new technology;- evaluate technology in use.

Data collection & analysis

• Observation & interviews– Notes, pictures, recordings– Video– Logging

• Analyses– Categorized– Categories can be provided by theory

• Grounded theory• Activity theory

Analytical Evaluation Overview

• Describe inspection methods.• Show how heuristic evaluation can be adapted to

evaluate different products.• Explain how to do doing heuristic evaluation and

walkthroughs.• Describe how to perform GOMS and Fitts’ Law, and

when to use them.• Discuss the advantages and disadvantages of

analytical evaluation.

Inspections• Several kinds.• Experts use their knowledge of users &

technology to review software usability.• Expert critiques (crits) can be formal or informal

reports.• Heuristic evaluation is a review guided by a set of

heuristics.• Walkthroughs involve stepping through a pre-

planned scenario noting potential problems.

Heuristic evaluation

• Developed Jacob Nielsen in the early 1990s.• Based on heuristics distilled from an empirical

analysis of 249 usability problems.• These heuristics have been revised for current

technology. • Heuristics being developed for mobile devices,

wearables, virtual worlds, etc.• Design guidelines form a basis for developing

heuristics.

Nielsen’s heuristics

• Visibility of system status.• Match between system and real world.• User control and freedom.• Consistency and standards.• Error prevention. • Recognition rather than recall.• Flexibility and efficiency of use.• Aesthetic and minimalist design.• Help users recognize, diagnose, recover from errors.• Help and documentation.

Discount evaluation

• Heuristic evaluation is referred to as discount evaluation when 5 evaluators are used.

• Empirical evidence suggests that on average 5 evaluators identify 75-80% of usability problems.

No. of evaluators & problems

3 stages for doing heuristic evaluation

• Briefing session to tell experts what to do.• Evaluation period of 1-2 hours in which:

– Each expert works separately;– Take one pass to get a feel for the product;– Take a second pass to focus on specific features.

• Debriefing session in which experts work together to prioritize problems.

Advantages and problems

• Few ethical & practical issues to consider because users not involved

• Can be difficult & expensive to find experts• Best experts have knowledge of application

domain & users• Biggest problems:

– Important problems may get missed– Many trivial problems are often identified– Experts have biases

Cognitive walkthroughs

• Focus on ease of learning• Designer presents an aspect of the design &

usage scenarios.• Expert is told the assumptions about user

population, context of use, task details.• One of more experts walk through the

design prototype with the scenario.• Experts are guided by 3 questions.

The 3 questions• Will the correct action be sufficiently evident to

the user?• Will the user notice that the correct action is

available? • Will the user associate and interpret the response

from the action correctly?

Note the connection to Norman’s gulf of execution and gulf of evaluation.

As the experts work through the scenario they note problems.

Pluralistic walkthrough

• Variation on the cognitive walkthrough theme.• Performed by a carefully managed team.• The panel of experts begins by working separately.• Then there is managed discussion that leads to

agreed decisions.• The approach lends itself well to participatory

design.

Predictive Models

• Provide a way of evaluating products or designs without directly involving users.

• Less expensive than user testing.• Usefulness limited to systems with

predictable tasks - e.g., telephone answering systems, mobiles, cell phones, etc.

• Based on expert error-free behavior.

GOMS

• Goals - the state the user wants to achieve e.g., find a website.

• Operators - the cognitive processes & physical actions needed to attain the goals, e.g., decide which search engine to use.

• Methods - the procedures for accomplishing the goals, e.g., drag mouse over field, type in keywords, press the go button.

• Selection rules - decide which method to select when there is more than one.

Use at NYNEX and NASA

Keystroke level model

• GOMS has also been developed to provide a quantitative model - the keystroke level model.

• The keystroke model allows predictions to be made about how long it takes an expert user to perform a task.

Response times for keystroke level operators (Card et al., 1983)

Operator Description Time (sec)K Pressing a single key or button

Average skilled typist (55 wpm)Average non-skilled typist (40 wpm)Pressing shift or control keyTypist unfamiliar with the keyboard

0.220.280.081.20

P

P1

Pointing with a mouse or other device on adisplay to select an object.This value is derived from Fitts’ Law which isdiscussed below.Clicking the mouse or similar device

0.40

0.20H Bring ‘home’ hands on the keyboard or other

device0.40

M Mentally prepare/respond 1.35R(t) The response time is counted only if it causes

the user to wait.t

Fitts’ Law (Fitts, 1954)

• Fitts’ Law predicts that the time to point at an object using a device is a function of the distance from the target object & the object’s size.

• The further away & the smaller the object, the longer the time to locate it and point to it.

• Fitts’ Law is useful for evaluating systems for which the time to locate an object is important, e.g., a cell phone,a handheld devices.

Characteristics of approaches

Usability testing

Field studies

Analytical

Users do task natural not involved

Location controlled natural anywhere

When prototype early prototype

Data quantitative qualitative problems

Feed back measures & errors

descriptions problems

Type applied naturalistic expert

Evaluation approaches and methods

Method Usability testing

Field studies

Analytical

Observing x x

Asking users

x x

Asking experts

x x

Testing x

Modeling x

Chapter 7

• Design in the marketplace• Featuritis• Timeline for moving from design to product• Incremental vs. radical design• As well as opinions related to

– New media– Augmented humans– Design and the environment

• The future of the Design of Everyday Things