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 (i.e. that your arrivals don’t consistently
outpace your closure, resulting in a high defect backlog), to determine the remaining defect backlog, to project the
future defect arrival/close rate up to and post-ship.
Measurement Method
Count
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Number of defects found and closed each unit of time (usually week, but could be day or month, depending on
iteration length). Graph over time, typically in 2 lines.
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Can also superimpose bars of “remaining defects” over the line graphs, as 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.)
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Total cumulative defects found and closed. Graph over time, typically in 2 lines. In this case, the difference
between the 2 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, should expect to see arrival rate slowing and closure rate surpassing it,
indicating that fewer defects are being found (hopefully because you’ve found them already) and any backlog or
outstanding defects are being fixed. If the arrival curve does not taper down, it suggests you may continue to find
defects post-ship. In the cumulative chart, expect to see the gap narrow between “total found” and “total fixed”. If a
large gap remains, you have many defects still not closed that may necessitate lengthening the schedule or shipping
with unclosed defects.
Note that looking purely at arrivals and closure 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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