Figure 5.5 shows two examples of histograms used for software project and quality management. Panel A shows the defect frequency of a product by severity level (from 1 to 4 with 1 being the most severe and 4 the least). Defects with different severity levels differ in their impact on customers. Less severe defects usually have circumventions available and to customers they mean inconvenience. In contrast, high-severity defects may cause system downtime and affect customers' business. Therefore, given the same defect rate (or number of defects), the defect severity histogram tells a lot more about the quality of the software. Panel B shows the frequency of defects during formal machine testing by number of days the defect reports have been opened (1 “7 days, 8 “14, 15 “21, 22 “28, 29 “35, and 36+). It reflects the response time in fixing defects during the formal testing phases; it is also a workload statement. Figure 5.6 shows the customer satisfaction profile of a software product in terms of very satisfied, satisfied, neutral, dissatisfied, and very dissatisfied. Although one can construct various metrics with regard to the categories of satisfaction level, a simple histogram conveys the complete information at a glance.

Figure 5.5. Two Histograms


Figure 5.6. Profile of Customer Satisfaction with a Software Product


As the examples show, the measurement scale of the data is either interval, ratio, or ordinal (reference the level of measurement discussions in section 3.2 of Chapter 3). If the measurement scale is nominal (e.g., types of software and models of development process), the ordering of the X-axis in a histogram no longer has significance. Such charts are commonly referred to as bar charts. Both histograms and bar charts are frequently used in software development.

What Is Software Quality?

Software Development Process Models

Fundamentals of Measurement Theory

Software Quality Metrics Overview

Applying the Seven Basic Quality Tools in Software Development

Defect Removal Effectiveness

The Rayleigh Model

Exponential Distribution and Reliability Growth Models

Quality Management Models

In-Process Metrics for Software Testing

Complexity Metrics and Models

Metrics and Lessons Learned for Object-Oriented Projects

Availability Metrics

Measuring and Analyzing Customer Satisfaction

Conducting In-Process Quality Assessments

Conducting Software Project Assessments

Dos and Donts of Software Process Improvement

Using Function Point Metrics to Measure Software Process Improvements

Concluding Remarks

A Project Assessment Questionnaire

Metrics and Models in Software Quality Engineering
Metrics and Models in Software Quality Engineering (2nd Edition)
ISBN: 0201729156
EAN: 2147483647
Year: 2001
Pages: 176

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