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Unit IV

Software Quality Improvement Techniques

Software systems have recently proliferated greatly and become a pervasive presenceboth in the life of individuals and in society at large. Accompanying the expansion of

software use, it is essential to ensure the high quality of software.

1. Sufficient software testing,2. Verification, and

. !ault elimination are the most important techniques for improving software quality.

"here are many methods for quality improvement. "hese cover product improvement,process improvement and people based improvement. #n the following list are methods of

quality management and techniques that incorporate and drive quality improvement$

1. #S% &''($2'') * guidelines for performance improvement.

2. #S% 1++'(($ 2''+ * information technology * process assessment * -art ($uidance on use for process improvement and process capability determination.

. /!0 * quality function deployment, also nown as the house of quality

approach.(. ai3en* 4apanese for change for the better5 the common 6nglish term is

continuous improvement.

+. 7ero 0efect -rogram * created by 869 9orporation of 4apan, based uponstatistical process controland one of the inputs for the inventors of Six Sigma.

:. Six Sigma* :;, Six Sigma combines established methods such as statistical

process control, design of experimentsand !Six Sigma?s0define, measure, analy3e, improve, control@ may be viewed as a

particular implementation of this.@

). /uality circle* a group >people oriented@ approach to improvement.&. "aguchi methods* statistical oriented methods including quality robustness,

quality loss function, and target specifications.

1'. "he "oyota -roduction System * rewored in the west intolean manufacturing.11. ansei 6ngineering* an approach that focuses on capturing customer emotional

feedbac about products to drive improvement.

12. "/< * total quality managementis a management strategy aimed at embeddingawareness of quality in all organi3ational processes. !irst promoted in 4apan with

the 0eming pri3e which was adopted and adapted in SA as the

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-roponents of each approach have sought to improve them as well as apply them for

small, medium and large gains. Simple one is -rocess Approach, which forms the basis

of #S% &''1$2'') /uality Big Bang type changes tend to fail more often compared to smaller changes@ and

adaption to enterprise cultures. !or example, quality circles do not wor well in everyenterprise >and are even discouraged by some managers@, and relatively few "/

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Statistical Software Quality Assurance Techniques

Ihat are the steps implied by statistical quality assuranceJ

1. #nformation about sHw defects, 2. An attempt is made to trace each defect to itsunderlying cause, . S/9A@ consists of three main parts.

1. Statistical -rocess 9ontrol >S-9@2. Acceptance Sampling >AS@

. 0esign of 6xperiments >0%6@ to improve quality and productivity.

Some terminolo!y" #n both S-9 and AS, samples are drawn. Although the terminology

is not uniform or universsal, we refer to the individuals sampled as units and to different

products in the line of goods made by a company as items. So we might say, DIe too asample of : units of #tem A and a sample of ) units of #tem B.D

Samplin! from a population vs" samplin! from a process" !rom the samples,decisions are made about the population or process generating the items maing up the

samples.

!or AS, there is a population of already produced items, called a lot.

!or S-9, there is no existing population5 rather, we are examining theprocess

generating the samples.

(1) Statistical Process Control

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standards to infer the quality of the lot from the quality of the sample. "he standards are

set according to what is required of the product. #n process control, depending upon the

application, there may be a standard, or you may Eust be monitoring the process to seethat there is no large deviation from what is usual and customary.

#ro$ucer%s ris& an$ consumer%s ris&9onsider the situation where each unit is either defective >not in conformance@ or oay.

Sampling will be used to estimate the proportion defective. Statistical methods are used

to set a sample sizeand an acceptance num'er" "he sample si3e is the number of unitsin the sample. "he acceptance number is the largest number of defectives in the sample

for which we still will accept the lot. #f the number of defectives in the sample is greater

than the acceptance number, the lot from which the sample came is reEected. "his entailstwo riss. "here is the ris that a good lot will yield a bad sample and hence lead to

reEection of the lot even though it is good. And there is the ris that a bad lot will yield a

good sample and hence lead to acceptance of the lot, even though it is bad. "he first risis called theproducer's risk >or seller?s ris@. "he second is the consumer's risk >or

buyer?s ris@. #n statistics these two types of error are called Type I and Type IIerrors.

(3) Design of Experiments

Approximately the last third of the course is focused on 0%6, the design of experiments

to achieve /uality Assurance through #mprovement by -lanned 6xperimentation. #nparticular, we will study the Analysis of Variance.

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Quality Appraisal #ro!rams

"he Appraisal -rogram oversees the quality and consistency of the Software ?s process

appraisal technology and encourages its effective use. #ts four main functions includecommunications to the appraisal community5 appraisal quality control5 training,

authori3ing, certifying, and providing resources for Nead Appraisers and "eam Neaders5

and monitoring and reporting appraisal results.

"hrough the S6# Appraisal -rogram, the highest quality candidates are selected andtrained as Nead Appraisers. %ngoing training and resources are provided for Nead

Appraisers.

Appraisal (lasses

!or benchmaring against other organi3ations, appraisals must result in consistent

ratings. "he S6# has developed a document to assist in identifying or developing

appraisal methods that are compatible with the 9

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S9Awhich are based on years of experience

in the process improvement community@ called appraisal method classes. Cequirements

are then allocated to each class as appropriate based on the attributes associated with thatclass. "hus, a particular appraisal method may be declared to be an AC9 9lass A, B, or 9

appraisal method. "his designation implies the sets of AC9 requirements that the method

developer has addressed when designing the method.

S(A#I 1ea$ Appraiser o$y of Knowle$!e ,S1A 2K-"he Standard 9

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successful S9A