Understanding exactly what is (and isn't) in the PDCA cycle is crucial for two reasons:

Implement the plan on a small scale. This is the testing phase where data is collected.

These are the first two steps of the DMAIC model. Because PDCA and DMAIC are both used for quality improvement, students often mix them up. PDCA is generally for iterative, smaller-scale improvements, while DMAIC is for more complex, data-heavy projects. Why the Distinction Matters