USABILITY COST-BENEFIT MODELS
Different Approaches to Usability Cost Analysis
Mikko Rajanen
Department of Information Processing Science, University of Oulu, PO Box 3000, FIN-90014, Oulu, Finland
Keywords: Usability, Usability Cost-Benefit Models, Cost of Usability.
Abstract: There are few development organizations that have integrated usability activities as an integral part of their
product development projects. One reason for this might be that the costs and benefits of usability activities
are not visible to the management. In this paper the author analyses some of the characteristics of the
published usability cost-benefit analysis models. These models have different approach for identifying the
costs of usability.
1 INTRODUCTION
Usability is defined as one of the main product
quality attributes for the international standard ISO
9126. It means the capability of the product to be
understood by, learned, used by and attractive to the
user, when used under specified conditions (ISO
9126, 2001). Another usually referred to definition
of usability is in standard ISO 9241-11, where
usability is defined as: “The extent to which a
product can be used by specified users to achieve
specified goals with effectiveness, efficiency and
satisfaction in a specified context of use” (ISO
13407, 1999).
Usability has many potential benefits for a
development organization such as increased
productivity and customer satisfaction. But even
today there are quite a few product development
organizations reportedly having incorporated
usability activities in their product development
process. Bringing usability activities into the product
development life cycle has been a challenge since
the beginning of usability activities over fifty years
ago (Ohnemus, 1996).
One reason for this is that the benefits of better
usability are not easily identified or calculated.
Usability engineering has been competing for
resources against other project groups who do have
objective cost-benefit data available for management
review (Karat, 1994). The purpose of this paper is to
categorise the usability cost-benefit analysis models
based on their approach for the usability cost
analysis. This broad topic is approached through a
following research question:
How do the usability cost-benefit models
approach and categorise the cost of better usability?
The cost-benefit analysis is a method of
analysing projects for investment purposes (Karat,
1994). It embodies the idea that decisions should be
based on comparing the advantages and
disadvantages of an action. Technical and financial
data is gathered and analysed about a given business
situation or function. This information assists in
decision making about resource allocation.
The method has three steps and it proceeds as
follows (Burrill and Ellsworth, 1980):
1. Identify the financial value of expected project
cost and benefit variables.
2. Analyse the relationship between expected costs
and benefits using simple or sophisticated
selection techniques.
3. Make the investment decision.
Development management often sees usability
activities as a potential risk to the deadline of their
projects. It is difficult to implement usability
activities in development projects without the
support of the business management. Management
level support for usability activities in development
projects is achieved if the benefits of better usability
can be identified and calculated. Better usability can
for example speed up the products market
introduction and acceptance (Conklin, 1991) and
increase revenues (Wixon and Jones, 1991). In the
usability cost-benefit analysis of usability activities,
332
Rajanen M. (2007).
USABILITY COST-BENEFIT MODELS - Different Approaches to Usability Cost Analysis.
In Proceedings of the Ninth International Conference on Enterprise Information Systems - HCI, pages 332-336
DOI: 10.5220/0002407803320336
Copyright
c
 SciTePress

expected costs (e.g., personnel costs) and benefits
(e.g., lower training costs) are identified and
quantified (Karat, 1994).
There are many published models for calculating
usability benefits, and as many ways of identifying
the benefits. A business benefit is a positive return
that the development organisation expects to obtain
as a result of an investment. There has been some
discussion in publications about the potential
business benefits of usability, but most of them are
focused on case studies of usability benefits or the
overall aspects of usability cost-benefit analysis. In
this research, the author analysed the differences and
characteristics between some of the published
usability cost-benefit models.
Calculating the cost of better usability is fairly
straightforward if the necessary usability tasks are
identified (Mayhew and Mantei, 1994). The actual
cost of usability can be divided into initial costs and
sustaining costs (Ehrlich and Rohn).
2 OVERVIEW OF USABILITY
COST-BENEFIT MODELS
There are surprisingly few published models for
analysing the benefits of usability in development
organizations. Most of the existing usability benefit
models analysed in this paper was selected from the
book Cost-Justifying Usability by Bias and Mayhew.
This book was published in 1994, but it is still the
best source of different usability cost-benefit
models. The analysed models taken from Cost-
Justifying Usability were selected for this report
because they represent the overall variety of
different views for usability benefit analysis. The
second edition of the book was published 2005 but it
did not change the usability cost-benefit models
(Bias and Mayhew 2005).
Bevan (Bevan, 2000) and Donahue (Donahue,
2001) have published two of the latest usability cost-
benefit analysis models. These models were selected
for this analysis because they have a slightly
different point of view on different benefits of
usability. The Bevan’s model also estimates
potential usability benefits in four different product
life cycles while other analysed models do not have
such a clear point of view about benefits in product
life cycles.
2.1 Ehrlich and Rohn
Ehrlich and Rohn analyse the potential benefits of
better usability from the point of the view of the
vendor company, corporate customer and end user
(Ehrlich and Rohn, 1994). They state that by
incorporating usability activities into a product
development project, both the company itself and its
customers gain benefits from within certain areas.
When compared to the other usability benefit models
analysed in this paper, Ehrlich and Rohn present the
most comprehensive discussion about different
aspects of usability cost-benefits.
According to Ehrlich and Rohn a vendor
company can identify benefits from three areas:
1. Increased sales
2. Reduced support costs
3. Reduced development costs.
In some cases, a link between better usability and
increased sales can be found, but usually it can be
difficult to relate the impact of better usability
directly to increased sales. One way to identify the
impact of usability on sales is to analyse how
important a role usability has in the buying decision.
The cost of product support can be surprisingly
high if there is a usability problem in an important
product feature, and the product has lots of users.
Better usability has a direct impact on the need for
product support and therefore, great savings can be
realized through a reduced need for support. By
focusing on better product usability and using
usability techniques, a vendor company can cut
development time and costs. The corporate customer
can expect benefits when a more usable product
reduces the time that end users need for training.
And in addition to official training, there are also
hidden costs for peer-support. End users often seek
help from their expert colleagues, who therefore
suffer in their productivity. It is estimated that this
kind of hidden support cost for every PC is between
$6.000 and $15.000 every year (Bulkeley, 1992).
End users are the final recipients of a more
usable product. According to Ehrlich and Rohn,
increased usability can result in higher productivity,
reduced learning time and a greater work satisfaction
for the end user. The end-user can benefit from
higher productivity when the most frequent tasks
take less time.
2.2 Bevan
Bevan estimated the potential benefits of better
usability for an organization to be during
USABILITY COST-BENEFIT MODELS - Different Approaches to Usability Cost Analysis
333

development, sales, use and support (Bevan, 2000).
A vendor can gain benefits in development, sales
and support. A customer can benefit in use and
support. When a system is developed for in-house
use, the organization can identify benefits for
development, use and support. In each category,
there are a number of possible individual benefits
where savings or increased revenue can be
identified. The total amount of benefits from better
usability can be calculated by adding all the
identified individual benefits together. Bevan mainly
discusses usability benefits derived from increased
sales, a lower need for training and increased
productivity. Benefits accruing due to decreased
development time are identified but they are not
discussed in detail.
2.3 Donahue
Donahue’s usability cost-benefit analysis model
(Donahue, 2001) is based on the model of Mayhew
& Mantei (Mayhew and Mantei, 1994). In this
model the costs and benefits of better usability are
analysed through costs for development organisation
and benefits for customer organisation. According to
Donahue the most important aspect of usability cost-
benefit analysis is calculating the savings in
development costs.
2.4 Karat
Karat approaches usability benefits through a cost-
benefit calculation of human factors at work (Karat,
1994). This viewpoint is different from other
analysed usability benefit models. There are some
examples of identified potential benefits. The
benefits are identified as:
– Increased sales
– Increased user productivity
– Decreased personnel cost through smaller staff
turnover.
A development organization can gain benefits
when better usability gives a competitive edge and
therefore increases product sales. A customer
organization can gain benefits when end user
productivity is increased through reduced task time
and when better usability reduces staff turnover.
Karat describes a usability cost-benefit analysis of
three steps. In the first step, all expected costs and
benefits are identified and quantified. In the second
step, the costs and benefits are categorized as
tangible and intangible. The intangible costs and
benefits are not easily measured, so they are moved
into a separate list. The third step is to determine a
financial value for all tangible costs and benefits.
Karat also links the usability cost-benefit analysis
with business cases. Business cases provide an
objective and explicit basis for making
organisational investment decisions (Karat, 1994).
2.5 Mayhew and Mantei
Mayhew and Mantei argue that a cost-benefit
analysis of usability is best made by focusing
attention on the benefits that are of the most interest
to the audience for the analysis (Mayhew and
Mantei, 1994). The relevant benefit categories for
the target audience are then selected, and the
benefits are estimated. Examples of relevant benefit
categories are given for a vendor company and
internal development organization. The vendor
company can benefit from:
– Increased sales
– Decreased customer support
– Making fewer changes in a late design life cycle
– Reduced cost of providing training.
The benefits for an internal development
organization can be estimated from the categories of
increased user productivity, decreased user errors,
decreased training costs, making fewer changes in a
late design life cycle and decreased user support. To
estimate each benefit, a unit of measurement is
chosen for the benefit. Then an assumption is made
concerning the magnitude of the benefit for each
unit of measurement. The number of units is then
multiplied by the estimated benefit per unit.
3 USABILITY COST FACTORS
The costs of better usability can be categorized into
three groups: one-time costs, recurring costs and
redesign costs. One-time costs or initial costs cover
for example the costs of establishing a laboratory for
usability testing. Recurring costs are for example the
salary costs of the usability professionals employed
in the usability testing laboratory. Redesign costs
cover the costs of redesigning the prototypes for
example based on the usability test results (Mayhew
and Mantei, 1994).
3.1 One-Time Costs
Ehrlich & Rohn, Mayhew & Mantei and Donahue
identify one-time costs and provide some example
calculations of one-time costs of usability work.
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These models do not provide further documentation
about an overall cost calculation. Karat identifies the
one-time costs but do not provide further
documentation or example calculations (Karat,
1994). Bevan does not identify one-time costs of
better usability at all (Bevan, 2000).
3.2 Recurring Costs
All of the analysed usability cost-benefit models
identify the recurring costs of better usability as one
factor in usability cost-benefit analysis. Ehrlich &
Rohn and Mayhew & Mantei provide some example
calculations and further discussion of recurring
costs. These models do not provide further
documentation about calculation of recurring
usability costs. Karat, Bevan and Donahue identify
the recurring costs of usability work but they do not
provide example calculations or further discussion
about cost calculation.
3.3 Redesign Costs
The costs of prototype redesign are different from
other two usability cost factors that these costs
usually affect a product development project
directly. For example the product development
project redesigns prototypes for the usability testing.
Mayhew & Mantei identify the prototype related
redesign costs and provide some example
calculations about this cost factor but there is no
further documentation about calculating the redesign
costs. Karat identifies this cost factor but does not
provide any example calculations or further
discussion.
3.4 Comparing the Usability
Cost-Benefit Models
There are some significant differences between the
analysed usability cost-benefit models in identifying,
documenting and providing example calculations for
one-time costs, recurring costs and prototype
redesign costs.
The comparison of the usability cost-benefit
models and cost factors presented above is
summarised in table 1.
Table 1: The extent of which the usability cost-benefit
models identify and document the costs of usability.
Cost factors
One-time
costs
Recurring
costs
Redesign
costs
Ehrlich &
Rohn
XX XX O
Bevan O X O
Donahue XX X O
Karat X X X
Mayhew &
Mantei
XX XX XX
XX = The usability cost factor are identified and
some example calculations are provided. No
further documentation how to do the calculations.
X = The usability cost factor are identified but no
example calculations or further documentation is
provided.
O = The usability cost factor is not identified.
4 CONCLUSIONS
There are few development organizations that have
integrated usability activities as an integral part of
their product development projects. One reason for
this might be that the costs and benefits of usability
activities are not visible to the management. In this
paper the author analysed how the published
usability cost-benefit analysis models identify and
document the usability cost factors.
None of the analysed usability cost-benefit
models cover the one-time costs factor fully by
identifying the cost, documenting the cost
calculation and providing some example
calculations. Ehrlich & Rohn, Donahue and Mayhew
& Mantei cover the one-time costs factor best
though they lack in either example calculations or
documentation. Karat identifies the one time costs
but does not provide either examples or further
discussion. Bevan does not identify one-time costs at
all.
None of the analysed usability cost-benefit
models cover the recurring costs factor fully. Ehrlich
& Rohn and Mayhew & Mantei cover the recurring
costs best though they lack in either example
calculations or further documentation. Bevan,
Donahue and Karat identify the recurring costs
factor but do not provide example calculations or
further discussion.
USABILITY COST-BENEFIT MODELS - Different Approaches to Usability Cost Analysis
335

None of the analysed usability cost-benefit
models cover the prototype redesign costs factor
fully. Mayhew and Mantei cover the redesign costs
factor best but lack in documenting the redesign cost
calculation. Karat identifies the prototype redesign
costs factor but does not provide example
calculations or further discussion about this cost
factor.
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