CS3100 Software Project Management Week 26 - Quality Dr Tracy Hall.
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Transcript of CS3100 Software Project Management Week 26 - Quality Dr Tracy Hall.
Slide 2
Learning outcomes
1. To understand the wider implications of quality
2. To understand the options to monitor and control it
Slide 4
What is Quality?…the totality of features and characteristics of a product or service that bears on its ability to satisfy stated or implied needs.
American Society of Quality
Degree to which a set of inherent characteristic fulfills requirements
ISO 9000
Fitness for purpose
Perceived Quality - Reputation
Slide 5
A wider view of qualityTime
BudgetQuality
Checks &feedback Inter-
operability
Ease of useError-free use
Clear interface
ImpactLiability
Standards
Profits
Maintenance
CompatibilityUpgrades
Reputation
Marketing No bugs
Well-codedGood design
interfaces
functions
features
reliability
speed
latency
Slide 6
Different perspectives
PEOPLE End User
Customer
Managing Director
Legal Team
Developer
What is quality from these
perspectives
Slide 7
Cost of prevention
amount spent to ensure work will be done correctly
includes risk reduction and error prevention
e.g. getting design right before production
activities may include supplier evaluation, training and staff development
Quality planning; formal technical reviews; test equipment; training
Cost
Defects
Time
What is the cost of quality?
Am
ount
Slide 8
appraisal costs association with
inspection and testing - company’s products- supplier’s products
e.g. testing, walkthroughs, design reviews
In-process and interprocess inspection; equipment calibration and maintenance; testing Cost
Defects
Time
Other costs associated with quality
Slide 9
internal failure cost of putting everything right while project still under
control (pre-delivery) re-coding software for problems found at internal
testing Rework; repair; failure mode analysis
external failure costs incurred post-delivery
- warranty/support costs- maintenance- handling complaints
lost future business Complaint resolution; product return and replacement;
help line support; warranty work
The killers
Slide 10
- A total of 7053 hours was spent inspecting 200,000 lines of code with the result that 3112 potential defects were prevented.
- Assuming a programmer cost of $40.00 per hour, the total cost of preventing 3112 defects was $282,120, or roughly $91.00 per defect.
- No inspections but that programmers had been extra careful and only one defect per 1000 lines of code escaped into the shipped product. That would mean that 200 defects would still have to be fixed in the field.
- At an estimated cost of $25,000 per field fix, the cost would be $5 million, or approximately 18 times more expensive than the total cost of the defect prevention effort
Internal failure
External failure
(Pressman 1997, p192)
Costs of avoiding poor quality
Slide 11
Attributes
portability
completeness
security
efficiency
reliability
speedmaintainability
usability
conciseness
Slide 12
How do we ensure quality?
Is it about measurement and process?
Can you measure quality?
Do you just check for quality at the end?
Slide 13
Prioritising problems
80:20 Rule
80% problems stem from 20% sources
Focus on the 20% first
But don’t neglect the other 80%
Slide 14
V Model
Quality Control throughout Software LifeCycle
unit test
integration test
systems test
acceptance testfeasibility
analysis
design
program specs
coding
Inspection stream
Testing stream
Slide 15
Other Processes
ISO 9000
CMM Software Engineering Institute
Motorola
TQM
Six Sigma
Look up some of these terms on the internet, academic papers etc.
Slide 16
ISO 9000
International Standard
Focusess
Documentation of Process
Documentation of Proof of Process
Requires Certification
Re-Certification
Slide 17
corporatequalitymanual
critical proceduresmanual
- corporate- divisional- functional
procedureguides documentation detailed work
instructions
policyobjectivesorganisationprimary functionsprocedures index
who does:whatwhenhowin what sequence
Quality management system structure (Cadle & Yeates p240)
Structure
Slide 18
planning a formal definition of how it will work
provides key reference point for project team members
acts as a bridge between customer and the supplier
provides a discipline and offers a framework against which issues can be considered and addressed before and during a project.
Quality Plans
Slide 19
CMM Capability Maturity Model
Level 1 - InitialUnpredictable and Poorly controlled
Level 2 - RepeatableAble to repeat previously mastered tasks
Level 3 - DefinedProcess is understood
Level 4 - ManagedProcess is measured and Controlled
Level 5 - OptimizingFocus on process improvement
Slide 20
TQM Total Quality Management
Total = Whole organisation
Encourage culture of achieving and
maintainting quality