Defects' Root Causes: PARETO Chart Technique

Considering that for a pool of defects, the root cause classification was performed using one technique or another - an example for doing this can be found here , it is the time now for deciding the priority of the root causes removal.

The best way to do this is to consider a PARETO chart in order to represent the classes of root causes:

Based on a chart like this, you can verify if you correctly defined the taxonomy for the root causes and/or the investigation of the root causes is correctly performed, since the 80-20 principle should be satisfied: 80 percent of the problems in a process result from just 20 percent of the causes.

After a short look at the PARETO representation, it shouldn't be difficult to decide which are root causes you want to adress 1st. In this example, ~61% of the defects are caused by the people (lack of) skills and the process (lack of process or improper use of process, etc). So, deriving corrective actions for these two causes and implementing them correctly will halve the number of defects in the future.

Finding the appropriate corrective actions is not an easy task and its success depends a lot on the skills of the people involved in deriving and implementing them.