Page 80 - DCAP305_PRINCIPLES_OF_SOFTWARE_ENGINEERING

Principles of Software Engineering

Notes Threat: The probability that an attack of certain type will happen over a period of time.
Security: The probability that an attack of certain type will be removed over a period of time.
Integrity = Summation [(1 - threat) X (1 - security)]

Usability
How usable is your software application? This important characteristic of your application is
measured in terms of the following characteristics:
• Physical / Intellectual skill required to learn the system.
• Time required becoming moderately efficient in the system.

• The net increase in productivity by use of the new system.
• Subjective assessment(usually in the form of questionnaire on the new system)
Standard for the Software Evaluation

In context of the Software Quality Metrics, one of the popular standards that address the
quality model, external metrics, internal metrics and the quality in use metrics for the software
development process is ISO 9126.
Defect Removal Efficiency
Defect Removal Efficiency (DRE) is a measure of the efficacy of your SQA activities. For e.g.
If the DRE is low during analysis and design, it means you should spend time improving the
way you conduct formal technical reviews.
DRE = E / (E + D)
Where E = No. of Errors found before delivery of the software and D = No. of Errors found
after delivery of the software.
Ideal value of DRE should be 1 which means no defects found. If you score low on DRE it means
to say you need to re-look at your existing process. In essence DRE is indicator of the filtering
ability of quality control and quality assurance activity. It encourages the team to find as many
defects before they are passed to the next activity stage. Some of the Metrics are listed out here:
Test Coverage = Number of units (KLOC/FP) tested/total size of the system

Number of tests per unit size = Number of test cases per KLOC/FP
Defects per size = Defects detected/system size
Cost to locate defect = Cost of testing/the number of defects located
Defects detected in testing = Defects detected in testing/total system defects

Defects detected in production = Defects detected in production/system size
Quality of Testing = No. of defects found during Testing/(No. of defects found
during testing + No. of acceptance defects found after
delivery) *100
System complaints = Number of third party complaints/Number of transactions
processed Effort Productivity = Test Planning Productivity
= No. of Test cases designed/Actual Effort for Design and
Documentation

Test Execution Productivity = No. of Test cycles executed/Actual Effort for testing
Test efficiency = (Number of tests required/The Number of system errors)

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