International Journal of Scientific & Engineering Research, Volume 4, Issue 12, December-2013 162

ISSN 2229-5518

Evaluation of Usability Using Soft Computing

Technique

Aishwarya Singh and Sanjay Kumar Dubey

Abstract— In the recent years, many factors have been recognised as an important contributor in evaluating software quality. Evaluating software is significant for managing, controlling and improving a software development life cycle. Quality of software cannot be measured easily, it depends on various factors. Usability is one of the chief quality factor and important aspect of software quality. This paper proposes a usability evaluation model using fuzzy multiple criteria weighted average approach. A case study is used to evaluate the usability of proposed model.

Index Terms— Usability, Quality model, Fuzzy, Software system, Soft Computing.

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1 INTRODUCTION

sability is a quality attribute that assesses how easy user interfaces are to use. The word ‘usability’ also refers to methods for improving ease-of-use during the design process [1]. It is the ability to provide good quality service. Since usability is fuzzy in nature, many models have been proposed over the years like McCall’s quality Model, Bohem’s quality model, FURPS quality models, ISO 9126 model etc.
enables quality to be designed into software product [3].

2 LITERATURE SURVEY ON USABILITY MODEL

Over the years, many methods and surveys have been per- formed in order to measure the usability of software system. It

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Each of these models explained and defined usability but still
they lacked in one way or another. ISO 9126-1 has represented
the latest research into characterizing software for the purpos-
es of software quality control, software quality assurance and
software process improvement [2].

Over the period of time, the demand for measurement of quality of software system has increased in order to meet the users demand and expectations. Measurement can be done at any stage of a software development. It is highly useful as it is
half times the cost to as much it will cost if the software fails. It provides a necessary feedback to check a software quality and find errors in it (if exists). Measurement of usability is quality measure of the product software and plays a vital role in giv- ing user an ease to use the software as well as the user’s satis- faction and reliability. This paper have made an attempt to add more attributes to the software quality factors, with the help of the quality factors already being stated in 9126-1 mod- el [4]. Paper proposes an integrated model that describes mul- tiple criteria on which usability depends. Fuzzy multi criteria approach is used to prove feasibility of the software quality factors. This is the approach taken with software qualities fac- tors such as functionality, efficiency and portability, and it
is part of usability inquiry in which surveys is a sub part. Sur-
vey is a method which focuses on problems and conclusions,
which is acquired from the collected information. It has been a
useful way to determine the usability in large group of users. Usability depends on certain factors which in turn depend on sub factors and which are further dependent on several char- acteristics. There is a hierarchy of structure which is designed
and shown in figure 1.

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• Aishwarya Singh is B.Tech (CS & E) from Amity University, Noida, India. Her research interst is in Human Computer Interaction and Software En- gineering.E-mail: aishwarya.singh969@gmail.com

• Sanjay Kumar Dubeu is Assitant Professor at Amity University, Noida,

Iindia. His research areas include Human Computer Interaction, Soft

Computing and Usability Engineering. He has published more than 75 re-

search papers in reputed National & International Journals. He has submit- ted his Ph. D. thesis in Computer Science and Engineering in Amity Uni-

versity Uttar Pradesh, India. E-mail: skdubey1@amity.edu.

Figure 1. Hierarchy Structure

3 EVALUATION STEPS OF USABILITY

Step 1. In the hierarchy structure, assign the fuzzy ratings (ri)

to all the leaf nodes.

Step 2. In the hierarchy structure again, assign the fuzzy weights (wi) to all the nodes (sub characteristics, characteristics).

Int 3

ISS

the Th the eva we we us

p value is calculat- uantify the usabil- d by the weighted

teristic_1) + r (char- (characteristic_n)*

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4 CASE STUDY

To evaluate the working of the usability model proposed above , a sample case study of MS POWER POINT 2007 has been choosen. The evaluation steps has been shown in the next paragraph.
A group of 5 users was made to fill a questionnaire in which the fuzzification criteria for the all the characteristics and sub factors were given. In the process of fuzzification , real time
values were assigned to the fuzzy sets. They are assigned as Very High (VH), High (H), Medium (M), Low(L) and Very Low (VL). These abbreviations are used throughout this sec- tion. The fuzzification criteria of language and fuzzification criteria of cultural conventions is reperseented in Table 2 and Table 3 respectively.
As discussed earlier ,each leaf node is associated with cor- responding rating and weight. The rating is the fuzzy value given by the user for a particular sub characteris- tic/characteristic/sub factor according to their usage of MS

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PowerPoint 2007. The weight is the fuzzy value given by the user for a particular sub characteristic/ characteristic / sub factor/factor according to its importance for calculating the usability.
For example, for the sub factor Simplicity, there is one characteristic universality .Universaliy is further dependent upon 2 sub characteristics, language and cultural conventions. The Triangular fuzzynumbers were assigned to fuzzy ratings and weights obtained by the users.
Similarly, Fuzzy ratings of (leaf nodes) Attractiveness, Op- erability, Understandability, Learnability and Usability Com- plaince were obtained and also the Fuzzy weights (sub charac- teristics, characteristics, sub factors, factors) were obtained.
The fuzzy weighted average of language and cultural con- ventions sub characteristics give the fuzzy rating for the cul- tural universality characteristic.
r(cultural conventions) = (0.0,0.25,0.5)*(0.5,0.7,0.9) + (0.0,0.25,0.5)*(0.5,0.7,0.9)
r(cultural conventions) = (0.0,0.36,0.9).
w(cultural conventions) is obtained from the users which is
(0.3,0.55,0.75).
The values of weights and ratings for Attractiveness leaf
nodes as obtained from 5 users are given in the Table 6 and
Table 7 respectively.
Similarly, we get the ratings and weights of other sub fac-
tors under Attractiveness shown in Table 8.
Now, to calculate the rating of the Attractiveness factor, the
fuzzy weighted average of these sub factors are taken. It is
calculated and the value is obtained and then the ratings of all
the five factors are calculated and the weights are obtained
from the users (Table 9).

+

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r(usability) = r (attractiveness) * w(attractiveness) + r (operabil- ity) * w(operability) + r (aunderstandability)* w(understandability) + r (learnability)* w(learnability) + r (usability compliance)* w(usability compliance).

r(usability) = (0.356,0.75,0.81)*(0.278,0.65,1.0) + (0.24,0.75,0.82)*(0.40,0.50,1.0) + ( 0.18,0.75,0.1)*(0.50,0.68,0.92)

+ (0.20,0.52,0.89)*(0.75,0.1,0.1)

+0.125,0.32,0.869)*(0.34,0.50,1.0)

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Line 1 Line 2

0 0.223 0.547 0.92 z

Figure 2. Fuzzy membership function for usability

Centroid Formula z* = ∫μ(z).z.dz
∫ μ(z).dz

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Where, z* is the defuzzified crisp value z is the value on x-axis and
μ(z) is the membership function.
Equation of Line 1 : 3.086z – 0.688 = μ
Equation of Line 2 : 2.466 – 2.681z = μ
Z* = ( ∫(3.086z – 0.688)z dz (z= 0.223 to 0.547) + ∫ (2.466 –
2.681z)z dz (z= 0.547 to 0.92)) / ∫ (3.086z – 0.688) dz
(z= 0.223 to 0.547) + ∫ (2.466 – 2.681z) dz (z= 0.547 to 0.92))
Z* = 0.562 (Software Usability)

4 CONCLUSION

This paper has represented the software quality parameters using the fuzzy multi criteria approach. In the recent years, many usability models has been proposed .As the factors of usability are fuzzy in nature, a lot of definitions has been giv- en which tend to overlap each other. In this paper, a detailed structure of usability model has been given for evaluating the software quality. This model describes the five factors given in
the ISO 9126-1 namely, attractiveness, operability, under-

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standability, learnability and usability compliance and a de-
tailed sub-factors structure on which these factors depend. For
the future, in the context of the usability model proposed
above, the authors will evaluate the usability of software sys-
tems.

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