Focus on Quality

You might assume that a software project can be shortened by spending less time on testing or technical reviews. "Needless overhead!" say people with a taste for code-and-fix development. Industry experience indicates otherwise. An attempt to trade quality for cost or schedule actually results in increased cost and a longer schedule.

As Figure 2-6 illustrates, projects that remove about 95 percent of their defects prior to release are the most productive; they spend the least time fixing their own defects. Beyond about 95 percent defect removal, projects have to expend extra effort to improve quality. Short of 95 percent, projects can become more efficient by removing more defects sooner. Approximately 75 percent of software projects presently fit into this category. For the projects in this category, the attempt to trade quality for cost or schedule is another example of fool's gold. It's also an example of a software project dynamic that isn't really new. IBM discovered 25 years ago that projects that focused their efforts on attaining the shortest schedules had high frequencies of cost and schedule overruns. Projects that focused on achieving low defect counts had the best schedules and the highest productivities.^[8]

Figure 2-6. Up to a point, the projects that achieve the lowest defect rates also achieve the shortest schedules. Most projects can shorten their schedules by focusing on fixing defects earlier.

Source: Adapted from Applied Software Measurement: Assuring Productivity and Quality, 2d Ed.^[7]