Hello everyone. Last time, I wrote about SIPOC as a tool that can be used for “scoping” in the first step of Lean Six Sigma, “Define”.
This time as well, I would like to write about CTQ, which is a tool used in “Define” to identify improvement opportunities within the company from VOC (voice of the customer).
1. What is CTQ?
“CTQ” is an acronym for “Critical To Quality”. You may be getting sick of all the 3-letter abbreviations:) Literally translated, it is like “important (thing) for quality”. It is sometimes referred to as “important quality characteristics”, but there seems to be no specific translation for it. It may not be well known among non-lean six sigma problem solvers:)
And what it is like is, as I wrote at the beginning, it is a tool that “identifies improvement opportunities within the company from VOC (voice of the customer)”.
In the past, I wrote that it is important to “collect facts” when solving problems, and I have written about research and analysis methods for that purpose on this blog. CTQ can also be said to be one of such analysis methods, but it is not a so-called quantitative analysis but a qualitative analysis method.
2. How to create CTQ – “CTQ tree”
Let’s create a CTQ using a simple example. The starting point will be the VOC. Here, let me put the example as “I want to drink delicious coffee as soon as I enter the shop” for easy understanding. Create a tree structure starting from this VOC. Therefore, it is sometimes called a “CTQ tree”. Let’s look at the image figure first.
VOC itself has many ambiguous expressions like this example, right? If we leave them as they are, we don’t know what and how much we need to achieve to satisfy the VOC. That’s where the CTQ tree comes in.
First, break VOCs down into “drivers”. Drivers are “elements to be achieved to satisfy VOC”. Here, it is broken down into two elements: “as soon as” and “delicious”. “CTQ” finally comes out from there. For “as soon as”, there is “within 5 minutes after ordering”, and for “Delicious”, there are “Temperature = 65 degrees”, “PH value = 9”. The important point of CTQ is to “quantify (as much as possible)” in this way.
When actually breaking down to the CTQ, it is of course important to talk to the appropriate stakeholders (experts) within the company, but it is also important to conduct customer surveys as necessary and thoroughly confirm them.
There is one more way to create CTQ, “Quality Functional Deployment (QFD)”. It feels messy, so I have rarely used it, but it might be good if you want to think more precisely. For your reference, let me put one link here.
3. Identify internal improvement opportunities from CTQ! – Cross-analysis of CTQ and business process
At the beginning, I wrote that CTQ is “a tool that identifies opportunities for improvement within the company from VOC (voice of the customer)”. From the CTQ tree in Figure 1, it seems that there are areas that need improvement, but in order to identify more specific opportunities for improvement, cross-analyze with business processes (I will write about process mapping later in this blog).
I would like to write business processes on the horizontal axis, so I rearranged the CTQs in Figure 1 on the vertical axis. We would identify improvement opportunities in this matrix of vertical: CTQ x horizontal: business process.
In this example, for “within 5 minutes after ordering”, the part that is handwritten when “telling the order to the kitchen” and the part that is left for a while after “the coffee is completed” are the bottleneck. Also, regarding “temperature = 65 degrees”, the part that is left for a while is an opportunity for improvement. Regarding “PH value = 9”, using tap water is an improvement opportunity. As an aside, the PH value of tap water in Japan is 7, and it is said that it is naturally suitable for coffee. A PH value of 9 means that the taste is milder in a more alkaline state.
When we look at it this way, the opportunities for improvement become much clearer, right?
That’s all for this time, and I would like to continue from the next time onwards. Thank you for reading until the end.