A recurring bone of contention between different schools of thought about performance measurement in the improvement world is the debate about quantitative versus qualitative analysis. Mark Graban’s recent book Measures of Success is an example of the quantitative approach, and this article by France Bergeron about Belts vs Lean represents the opposing view.

To be sure, “Belts vs Lean” is not quite the same as quantitative vs qualitative. “Belts” is a term that has come to signify the technical expertise to design and do rigorous experiments using statistical analysis. A common critique from this perspective is that the simpler method of interpreting trends on green and red bar charts against target is an unscientific, and therefore unreliable, approach to understanding the data.

However, there is more to this than meets the eye.

The graph below was one of the first graphs the team in the diabetic outpatients’ clinic at Groote Schuur hospital put on their visual board. They are in their first year of their journey to implement a Daily Management System.

The team set the target at not more than 20 patients per clinic per day because there were always more patients than they could cope with and many patients ended up on a long waiting list. In addition, the computerised booking system was set to allow only 20 patients per clinic per day.

Clearly this was a defensive target that came from the perspective of the team’s concerns about the pressures they were working under. As facilitators supporting the diabetics team in their journey we were troubled by this target that did not reflect the patient’s perspective who as the customer of the process were entitled to a more timeous service. However, we were aware of the difficult circumstances that the staff were working in and did not think that the time was right to address the issue with them.

Then one day the following graph appeared on their board. At first sight the immediate question is what is going on here? Did they lose the plot about which side of the target line should be red?


What actually happened is that the team decided that despite the pressures on them they needed to change their target to servicing at least 30 patients a day to improve their service delivery. That necessitated the change in colour from red to green because they had to exceed 30 patients per day to achieve target.

This might seem like a minor technical issue, but actually it represents a huge shift in mindset. The first principle of Lean Thinking is to focus on creating value for your customers. What this graph shows is that this team made that mind-shift. Quantitative analysis of graphs can tell us many interesting things, but sometimes the story that the graph by itself cannot tell us is way more important.

The Cynefin framework (see below) helps us to cope with the different kinds of problems that we need to manage in this volatile, uncertain, complex, ambiguous world that we live and work in. It seems to me that quantitative statistical analysis works best in the complicated quadrant where technical expertise is necessary to uncover the causal relationship. Unfortunately, the technical expertise required intimidates many people and demotivates them from trying to use it. However, a simple way of depicting a trend against a target with red and green bars can go beyond known solutions. Merely by moving people to experiment with improvement actions it can precipitate unexpected complex effects such as a change in mindset.

So for what it is worth, my take on this bone of contention is that the most useful approach to use is the one that is most appropriate to the people and the circumstances where it is used. The simplest method of visualising their data was the best method for the diabetic clinic team, because it facilitated their engagement and led to a deep insight into a foundational principle of Lean Management.

The good news is that the recent publication of “Four Types of Problems” by Art Smalley contains a wealth of information about how to use A3 thinking for the different levels of problems we encounter. I have no doubt that it will become an invaluable resource as lean practitioners graduate from A3 problem-solving at an operational level to tackle systemic and strategic problems at higher levels of management.

Please let us know your thoughts on the topic and what works for you.