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Ch 10 cost of software quality
 

Ch 10 cost of software quality

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    Ch 10 cost of software quality Ch 10 cost of software quality Presentation Transcript

    • Software Engineering College of Arts, Media and Technology ,CMU. Kittitouch S. 1.1-20-2-12
    • version Change detail Release date Author 1.0 - 17-2-12 Kittitouch 1.1 Add page 32,33,36 20-2-12 Kittitouch
    •    Objectives of cost of software quality metrics The classic model of cost of software quality Application of a cost of software quality system
    • To be completed There are about ‘Y errors’ per 1000 lines of code It takes about ‘Z minutes’ to find each error It takes about ‘U hours’ to fix each error
    • There are about ‘5 to 15 errors’ per 1000 lines of code It takes about ‘75 minutes’ to find each error It takes about ‘2 to 9 hours’ to fix each error
    • Managerial control over the cost of software quality is achieved by comparison of actual performance figures with:  Control budgeted expenditures (for SQA prevention and appraisal activities)  Previous year’s failure costs  Previous project’s quality costs (control costs and failure costs)  Other department’s quality costs (control costs and failure costs)
    •  Control organization-initiated costs to prevent and detect software errors  Evaluation of the economic damages of software failures as a basis for revising the SQA budget  Evaluation of plans to increase or decrease SQA activities or to invest in a new or updated SQA infrastructure on the basis of past economic performance
    • The model classifies costs related to product quality into two general classes:  Costs of control include costs that are spent to prevent and detect software errors in order to reduce them to an accepted level.  Costs of failure of control include costs of failures that occurred because of failure to prevent and detect software errors. The model further subdivides these into subclasses.
    • Costs of control are assigned to either the prevention or the appraisal costs subclass:  Prevention costs include investments in quality infrastructure and quality activities that are not directed to a specific project or system, being general to the organization.  Appraisal costs include the costs of activities performed for a specific project or software system for the purpose of detecting software errors.
    • Failures of control costs are further classified into internal failure costs and external failure costs:  Internal failure costs include costs of correcting errors that have been detected by design reviews, software tests and acceptance tests (carried out by the customer) and completed before the software is installed at customer sites.
    •  External failure costs include all costs of correcting failures detected by customers or the maintenance team after the software system has been installed.
    •  Prevention costs include investments in establishing a software quality infrastructure, updating and improving that infrastructure as well as performing the regular activities required for its operation.
    • 1. Investments in development of new or improved SQA infrastructure components or, alternatively, regular updating of those components:  Procedures and work instructions  Support devices: templates, checklists, etc.  Software configuration management system  Software quality metrics
    • 2. Regular implementation of SQA preventive activities:     Instruction of new employees in SQA subjects and procedures related to their positions Instruction of employees in new and updated SQA subjects and procedures Certification of employees for positions that require special certification Consultations on SQA issues provided to team leaders and others.
    • 3. Control of the SQA system through performance of:    Internal quality reviews External quality audits by customers and SQA system certification organizations Management quality reviews
    • Appraisal costs are devoted to detection of software errors in specific projects or software systems.  Typical appraisal costs cover: 1. Reviews:  Formal design reviews (DRs)  Peer reviews (inspections and walkthroughs)  Expert reviews.
    • 2. Costs of software testing:     Unit tests Integration tests Software system tests Acceptance tests (participation in tests carried out by the customer).
    • 3. Costs of assuring quality of external participants, primarily by means of design reviews and software testing. These activities are applied to the activities performed by:  Subcontractors  Suppliers of COTS (Commercial Off-The-Shelf)software systems and reusable software modules  The customer as a participant in performing the project.
    •  External failure costs entail the costs of correcting failures detected by customers or maintenance teams after the software system has been installed at customer sites.
    •  Internal failure costs are those incurred when correcting errors that have been detected by design reviews, software tests and acceptance tests performed before the software has been installed at customer sites.  Internal failure costs represent the costs of error correction subsequent to formal examinations of the software during its development.
    •    Costs of redesign or design corrections subsequent to design review and test findings Costs of re-programming or correcting programs in response to test findings Costs of repeated design review and retesting (regression tests).
    •  Resolution of customer complaints during the warranty period.  Correction of software bugs detected during regular operation.  Correction of software failures after the warranty period is over even if the correction is not covered by the warranty.
    •      Costs of carrying out contract reviews Costs of preparing project plans, including quality plans Costs of periodic updating of project and quality plans Costs of performing regular progress control Costs of performing regular progress control of external participants’ contributions to projects
    •   Unplanned costs for professional and other resources, resulting from underestimation of the resources in the proposal stage. Damages paid to customers as compensation for late project completion, a result of the unrealistic schedule in the Company’s proposal.
    •   Damages paid to customers as compensation for late completion of the project, a result of management’s failure to recruit team members. Domino effect: Damages to other projects planned to be performed by the same teams involved in the delayed projects. The domino effect may induce considerable hidden external failure costs.
    •  • • • • • • • • • • Types of costs absorbed by the customer who buys a defective product. Wasted time Lost data Lost business Frustrated employees quit Demos or presentations to potential customers fail because of the software Cost of replacing product Cost of reconfiguring the system Cost of tech support Injury / death Cost of bad publicity
    •  IEEE -(Institute of Electrical and Electronics Engineers) Computer Society  ISO - (International Organization for Standardization)  DOD -(US Department of Defense)  ANSI -(American National Standards Institute)  IEC -(International Electro technical Commission)  EIA -(Electronic Industries Association).
    •    ISO/IEC 9000-3 – Quality certification standards for software development and maintenance organizations ISO/IEC 15504 – Organizational software process capability/capacity Assessment ISO/IEC/IEEE 12207 – Software development practices.
    • ISO/IEC29110 Standard Suitable for very small entity >>> not over 25 people Statement of Work Project Management Basic profile Software Implementation Software Configuration
    •  Chapter 22:Daniel Galin. SOFTWARE QUALITY ASSURANCE From theory to implementation. Pearson Education Limited,2004.  Costs and Benefits of Quality :Claude Y Laporte,SQA.,2009