Defect Trends |
This guideline describes how to measure and use defect arrival and close trends.
Relationships
Related Elements | Defect Density at Customer Ship
Main Description
### Overview This is a trend chart showing the rate of defects arrival and closure (fixing) over the project duration. Use this chart to ensure that arrival and closure rates have some correlation (in other words, that your arrivals do not consistently outpace your closure, resulting in a high defect backlog). You can also use this chart to determine the remaining defect backlog, and to project the future defect arrival and close rate up to and including the post-ship phase. ### Measurement Method Count Number of defects found and closed each unit of time (usually a week, but could be a day or month, depending on your iteration length). This is a graph over time, typically in two lines. You can also superimpose bars of `remaining defects` over the line graphs, because this may not always be evident. (The close rate can exceed the arrival rate for one or more data points, which can obscure the backlog.) Total cumulative defects found and closed. This is a graph over time, typically in two lines. In this case, the difference between the two lines shows the defects remaining (not including any backlog that predates the collection of arrivals.) ### Measurement Analysis As the end of cycle (ship date) nears, you should expect to see the arrival rate slowing and the closure rate surpassing it. This indicates that fewer defects are being found (hopefully because you have found them already), and that any backlog or outstanding defects are being fixed. If the arrival curve does not taper down, it suggests that you may continue to find defects post-ship. In the cumulative chart, you expect to see the gap between `total found` and `total fixed`. If a large gap remains, you have many defects that are still not closed: this may necessitate lengthening the schedul,e or shipping with unclosed defects. Note that looking purely at arrivals and closures does not include defects in a backlog that predates the data collection. Use this metrics in conjunction with Defect Density at Customer Ship
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