In the context of the CMMI, CAR is a Maturity Level 5 Process Area. You can perform CAR qualitatively at lower Maturity Levels, but you cannot realize the full benefits of CAR until you have stable processes and statistically understand the process capabilities. Let’s step through the practices one-by-one and talk about what they mean from a quantitative perspective;
SP 1.1 Select the defects and other problems for analysis.
You can perform this practice very simply and qualitatively just by having a gut feel that something is wrong and you want to investigate its causes. However, you should be using data and statistical tools such as Pareto analysis, histograms, or process capability analysis to determine which defects to analyze.
SP 1.2 Perform causal analysis of selected defects and other problems and propose actions to address them.
You can perform this practice qualitatively just by meeting with those people responsible for performing the process, using tools like cause-and-effect (fishbone) diagrams or check sheets. From a Maturity Level 5 perspective, you may have criteria that states you perform causal analysis when a stable process does not quantitatively meet its specified quality and process performance objective.
SP 2.1 Implement the selected action proposals that were developed in causal analysis.
Again it is possible to perform this practice qualitatively simply by implementing an action as the result of the cause-and-effect diagram. From a Maturity Level 5 perspective, you may be designing an experiment to see if the proposed action will have the desired quantitative results.
SP 2.2 Evaluate the effect of the changes on process performance.
This practice will be difficult to perform qualitatively. The intent of this practice is to measure the effects of the change on the process performance, which can only be done accurately if you have stable and capable processes in place and you are using quantitative methods to manage these processes.
SP 2.3 Record causal analysis and resolution data for use across the projects and organization.
If you are performing qualitative causal analysis you may not have any data to record other than results from the cause-and-effect diagram and rationale for the change. From a Maturity Level 5 perspective you might have data on the defects and other problems you analyzed and measures of the changes to the process performance resulting from the causal analysis.