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Gary A. GackMBA, Six Sigma Black Belt, ASQ Certified Software Quality Engineer
(1) it serves a valid organizational purpose - efforts are made to quantify this aspect of effectiveness with return on
investment estimates, yet it is essentially a subjective evaluation.
(2) it is acceptably defect free. The term “defect” in this context is intended to be broadly construed
• e.g., a missed or incorrect requirement is a defect; a user-unfriendly design is a defect.
• Hence, once a project has been initiated the effectiveness of the software process used to execute the project is appropriately measured by defect containment – i.e., the percentage of defects removed before the software product is delivered to the customer.
• In many software groups finding and fixing defects consumes 50-70% of total cost – Best practice groups reduce that by at least 50%
• Models allow you to think through the consequences of alternative strategies … quickly, at very low cost
• Models allow you to forecast both quality and financial consequences of alternatives– Creating a business case in the process– Creating a basis for “quality adjusted” status evaluation
• Modeling motivates measurement and “management by fact”
• Predict (1) delivered quality and (2) total non-value-added effort (cost)• Predict defect “insertion”
– Focus attention on defects, which account for the largest share of total development cost.
– Enable early monitoring of the relationship between defects likely to be present and those actually found – provide early awareness.
• Estimate effort needed to execute the volume of appraisal necessary to find the number of defects we forecast to remove. – a ‘sanity check’ on the planned level of appraisal effort – i.e., is it actually
plausible to remove an acceptable volume of defects with the level of effort planned?
• Forecast both “pre-release” (before delivery) and “post-release” (after delivery) NVA effort. – When delivered quality is poor, post-release defect repair costs can be 50%