Continual or continuous improvement?

As a quality professional, you have surely heard of the requirement for continual improvement. Or is it continuous? Hmm…

Is there a difference, or are we just splitting hairs? Plenty of people use ‘continual’ and ‘continuous’ interchangeably, much like ‘preventive’ and ‘preventative’…

As I teach this part of the course, my students almost invariably gloss over the difference, generally using the more familiar term and talking about ‘continuous’ improvement.

In actuality, there is a distinction, and not without a difference.

Let us start with the ultimate source of wisdom in our business (bow your head or roll your eyes, your choice): Under clause 5.2.1.d, ISO 9001:2015 requires organizations to establish a quality policy that “includes a commitment to continual improvement of the quality management system.”

So, we should use ‘continual’ because the Standard says so. End of discussion, right? Well, yes, but there is also a better reason.

Personally, I have done this work long enough, and drank so much Kool-Aid along the way, that I find the Standard generally makes sense, and there is a good reason it is written a particular way. It is possible to ask why the standard imposes a particular requirement, and actually expect a sensible answer.

‘Continuous’ is something that is always happening, while ‘continual’ is a recurring event, meaning that it happens occasionally, but is not happening at every point in time.

An analogy may be helpful:

Every point in a ramp is going up, in a continuous way.

In a staircase, all points on any given step are at the same level. Yet, as we go from one step to the next, there is a sudden jump to a different level, and this happens repeatedly, in a continual way.

The idea of continual improvement is closely related to the P-D-C-A cycle, which is discussed in clause 0.3.2 of the Standard. (Yes, there is life before Clause 4, and the Introduction -Clause 0- is a great read.)

Under P-D-C-A, we are expected to start with an action plan (plan), then implement it (do), while monitoring performance (check). Once the process has run for some time, we should use the data we collected to find ways to improve it (act). We then prepare a plan to implement those improvements, and the cycle continues.

In this way, we have periods when the process runs smoothly, with recurring jumps in performance as a result of implementing improvements. In other words, the P-D-C-A cycle drives the periodic implementation of incremental improvements – ‘continual’ improvement!

On the other hand, if we tried to implement a ‘continuous’ improvement model, we would have to always deploy changes. The process would never stabilize and there would never be an opportunity to collect data and plan the next move. The result would be chaos, just the opposite of improvement.

Now go forth and prevent.