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SQA for Individuals

Date post: 08-Feb-2016
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SQA for Individuals. based on "A Personal Commitment to Software Quality" by W.S. Humphrey SEI at Carnegie Mellon University. Reasons for Looking at the Individual. The root cause of all software defects is humans. Software productivity declines as product size increases. - PowerPoint PPT Presentation
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based on "A Personal Commitment to Software Quality" by W.S. Humphrey SEI at Carnegie Mellon University
Transcript
Page 1: SQA for Individuals

based on"A Personal Commitment to Software Quality"

by W.S. HumphreySEI at Carnegie Mellon University

Page 2: SQA for Individuals

The root cause of all software defects is humans.

Software productivity declines as product size increases. Increased complexity makes debugging

difficult, so more time is spent in testing.

If the all individual parts are of very high quality, your process can scale up with little reduction in productivity.

Page 3: SQA for Individuals

Most Important must provide necessary functions to the

user includes usability and convenience

Second Most Important: the product must work

Distance Third… compatibility, and all the other "ilities"

Page 4: SQA for Individuals

Schedules built on unreliable data force developers to spend much time reacting to crises. No time to do much if any QA

hence, biggest budget item is usually Testing

Stuck in rut of "test, debug, fix, repeat"

Experimenting is a risk

Developers have no data on the number of defects they inject or the costs of fixing those defects.

Page 5: SQA for Individuals

1. Determining that there is a problem2. Isolating the source of the problem3. Determining exactly what is wrong4. Fixing the Requirements5. Fixing the Design6. Fixing the Implementation7. Inspecting and Testing the fix8. Testing the fix to ensure it doesn't cause other

problems9. Changing the Documentation to reflect the fix

Page 6: SQA for Individuals

IBM (relative costs) during design $1.5 prior to coding $1 during coding $1.5 during test $60 in field use $100

Reviews are 2 or 3 times as efficient as testing at finding defects.

Combined design and code reviews have a yield of 60% to 80%.

Page 7: SQA for Individuals

Without any QA 50 KLOC with 2500 defects to be found average 4 hours of work per defect 10,000 hours10,000 hours to remove defects

With Reviews 50 KLOC with 2500 defects 70% of defects removed via Reviews

average 0.5 hours per defect 875 hours of work

remaining 750 defects average 8 hours each 6000 hours

Total = 6,875 hours6,875 hours

Page 8: SQA for Individuals

Failure Costs total time in compile and test

few developers count defects found during compile and individual unit testing

Appraisal Costs time spent in design and code reviews any inspection time

Prevention Costs prototype development casual analysis meetings process improvement actions or meetings

Page 9: SQA for Individuals

Yield (step n) = 100 * (defects removed in step n) (defects removed in n + defects escaping n)

Goals, perform small experiments to improve the yield of filters reduce the # of defects injected improve productivity

measured in LOC produced per month productivity increase comes from less time spent in

testing


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