Additionally to root cause analyses of defects (see: Defects can help creating quality) steady measurements and benchmarks are an
important basis for continuous improvements. The following three metrics can
already cover the most important aspects:
- Productivity (Cost Efficiency): The performance of the development process until the achievement of a predefined (outer and inner) quality ready for delivery (see: Measuring Productivity in Software Development).
- Defect Rate (Defect Density): The quotient from the number of production defects per time unit and the size of the system. It must be defined which types of defects are relevant for the defect rate.
- Maintenance Effort/Costs: The quotient from the effort for maintenance tasks per time unit and the size of the system. Ideally differentiated according to task types as defect analysis, defect correction, advisory services, etc.
For each of these aspects target values resp.
thresholds (baselines) are important, where exceeding indicates a need for clarification
or, in the next step, a need for immediate action. Finding these thresholds will
be facilitated through benchmarks of different systems, projects or shops,
where measurements will be performed by using exactly the same methods.
The easiest way is using the mean value or, if extreme
values shall not be considered, the median as a threshold. In cases where a
measured value is worse than the mean value or the median of all values an
analysis or assessment helps finding the root causes. Mostly root causes lead to
improvement measures. Their effectiveness becomes transparent by the
course of subsequent measurements.
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