quality concept
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Quality Concept. Computer Science Department, Faculty Of Science Prince of Songkhla University Apirada Thadadech. Content. How is measures quality? Cost of quality The quality triangle Type of software quality. How is measures quality?. - PowerPoint PPT PresentationTRANSCRIPT
Quality ConceptQuality Concept
Computer Science Department, Faculty Of Science Computer Science Department, Faculty Of Science Prince of Songkhla UniversityPrince of Songkhla University
Apirada ThadadechApirada Thadadech
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ContentContent
How is measures quality?How is measures quality? Cost of qualityCost of quality The quality triangleThe quality triangle Type of software qualityType of software quality
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How is measures quality?How is measures quality?
Quality is frequently associated with some Quality is frequently associated with some measure of :measure of : Goodness, Goodness, Excellence Excellence LuxuryLuxury
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How is measures quality?How is measures quality?(next)(next)
There are 4 other, equally valid perspectives:There are 4 other, equally valid perspectives:1.1. The user’ s perspective : Product is fitness for The user’ s perspective : Product is fitness for
requirements.requirements.2.2. The manufacturer’s : how well a product The manufacturer’s : how well a product
conform to specification.conform to specification.3.3. The product perspective: measurable The product perspective: measurable
attributes of a product.attributes of a product.4.4. The value-based perspective: whatThe value-based perspective: what a a
customer is willing to pay for quality.customer is willing to pay for quality.
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DefectsDefects EffortEffort
UserUser Delivered defectsDelivered defects Wasted timeWasted time
ManufacturerManufacturer Defect injection rateDefect injection rateDefect removal efficiencyDefect removal efficiency
Defect preventionDefect preventionQuality appraisal reworkQuality appraisal reworkCustomer supportCustomer supportComplaint handlingComplaint handlingProduct recallProduct recallWarranty claimsWarranty claims
ProductProduct Number of defectsNumber of defects
Defect densityDefect density
ReworkReworkScrapScrap
ValueValue Cost of defective productCost of defective product Cost of quality relate Cost of quality relate activitiesactivities
Table Of Quality Measures
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Cost of qualityCost of qualityThere are 2 major elementsThere are 2 major elements1.1. The cost of quality improvement: associated with activities (Table 1) The cost of quality improvement: associated with activities (Table 1)
Defect prevention
Appraisal
2.2. The cost of failure : fails to meet its quality requirements (Table 2)The cost of failure : fails to meet its quality requirements (Table 2)
Internal failure – prior to transfer of ownership to the customer
External failure – after transfer of ownership to the customer
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Table 1 Typical quality improvement costsTable 1 Typical quality improvement costs
Defect PreventionDefect Prevention AppraisalAppraisal
Quality planningQuality planningQuality auditingQuality auditingReviewing & verifying Reviewing & verifying designsdesignsQuality trainingQuality trainingAcquisition, Analysis and Acquisition, Analysis and report of quality datareport of quality dataProduct recall insuranceProduct recall insurance
Design appraisalDesign appraisalReceiving and inspectionReceiving and inspectionInspection and testingInspection and testingAnalysis and reporting of test Analysis and reporting of test and inspection resultsand inspection resultsRecord storage of quality Record storage of quality documentsdocuments
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Table 2 Typical quality failure costsTable 2 Typical quality failure costs
Internal FailureInternal Failure External FailureExternal Failure
ScrapScrapReplacement, rework Replacement, rework and repairand repairDefect diagnosisDefect diagnosisDowntimeDowntime
ComplaintsComplaintsSupportSupportWarranty claimsWarranty claimsProducts rejected and Products rejected and returnedreturnedConcessionsConcessionsLoss of salesLoss of salesRecall costsRecall costsProduct reliabilityProduct reliability
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Cost of Quality CurveCost of Quality Curve
0%0% 100%100%
Cos
tC
ost
QualityQuality
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The quality triangleThe quality triangle
Products can suffer from poor quality in Products can suffer from poor quality in number of different ways:number of different ways: User’s viewUser’s view Product’s viewProduct’s view Manufacturer’s viewManufacturer’s view
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The Quality TriangleThe Quality Triangle
GapGap
Product View
product
User Requirements
User’s View
Specification
Manufacturer’s View
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User Requirement – Specification gapUser Requirement – Specification gap
Misunderstood requirementsMisunderstood requirements Ignored Ignored requirementsrequirements Missing requirementsMissing requirements Outdated requirementsOutdated requirements Unneeded requirementsUnneeded requirements
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Specification – Product GapSpecification – Product Gap
Wrong interpretation of requirement cause of Wrong interpretation of requirement cause of ambiguity in specificationambiguity in specification
Requirements identified after development Requirements identified after development commentedcommented
Changes to specified requirements identified Changes to specified requirements identified after development commentedafter development commented
Features added by the developers follow Features added by the developers follow technicaltechnical
Requirements ignored by the developers cause Requirements ignored by the developers cause of they were too difficult to implementof they were too difficult to implement
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Product – User Requirement GapProduct – User Requirement Gap
The gap is directly dependent on 2 side The gap is directly dependent on 2 side of triangleof triangle If two sides are short, then this gap will be If two sides are short, then this gap will be
smallsmall
If two sides are long, then this gap will be If two sides are long, then this gap will be largelarge
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The Quality TriangleThe Quality Triangle
Pro
duct
Pro
duct
Specification
Specification
User
User R
equirements
Requirements
If the quality better If the quality better aligned the triangle aligned the triangle will become smallerwill become smaller
If all view are If all view are perfectly aligned, it perfectly aligned, it will be represented will be represented by a single dot. by a single dot.
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Quality triangle shapesQuality triangle shapes
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Quality triangle shapesQuality triangle shapes
Poor understanding of REQ. Poor understanding of REQ. corrected during SW corrected during SW development :SW meets REQdevelopment :SW meets REQ
GoodGood understanding of REQ. understanding of REQ. poor SW development : SW not poor SW development : SW not meets REQmeets REQ
Poor understanding of REQPoor understanding of REQ
good SW development : SW good SW development : SW not meets REQnot meets REQ
Poor understanding of REQPoor understanding of REQ
poor SW development : SW not poor SW development : SW not meets REQmeets REQ
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Software Product MeasurementSoftware Product Measurement
In Table list a number of the more popular measures of Software Product quality
The ISO 9126 Standard for Software The ISO 9126 Standard for Software Product QualityProduct Quality
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Software QualitySoftware Quality
External QualityExternal Quality Internal QualityInternal Quality Quality in UseQuality in Use
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The Quality TriangleThe Quality Triangle
product
User RequirementsUser Requirements SpecificationSpecification
External External QualityQuality
Internal Internal QualityQuality
Quality in Use