What Does CTQ Mean?

Designers have to set priorities. What is most important to ensure customer satisfaction is called Critical to Quality, or CTQ. If executed correctly, it provides the edge that allows your product to stand out amongst competitors.

Here are two common ways this plays out:

  1. When designing a new product, the designer indicates what characteristics of that product are most important.
  2. When planning for a manufacturing process, they indicate what steps of that process need the most attention when it comes to equipment maintenance, staff training, and process control.

It is crucial that the rest of the team knows what is Critical to Quality, otherwise, the New Product Development is less likely to be a success.

The terms ‘Quality’ and ‘Critical to Quality’ are two different things. We all know that it is important to produce a “quality product”, but all too often the focus is placed on the actual dimension, surface finish, or some other attribute that the design team thinks is important in creating that “quality product”.

Two examples of a CTQ product characteristic

Example 1: electric vehicles (EVs)
One of the main sources of anxiety of EVs is short range (and the inability to go to their destination without prolonged stops or even serious detours). The Tesla Model S Plaid promises 396 miles of range as of April 2022. It is one of its major advantages over the competition.

Example 2: LEGO bricks
LEGO bricks have to fit into each other consistently. That’s their main function. They have to get fastened and remain fastened when subjected to a certain force, and they need to get separated easily.
The two dimensions I represented in the image below have to be consistently on target. They are CTQ and they must be labeled as such on the 2D CAD drawings of the parts.

Lego Critical Characteristics

An example of a CTQ process step

When a process or a quality engineer sets up a process control plan, she starts with a list of the process steps. And, for each of them, she has to assign a letter (usually from A to D, and often called “class” or “special characteristic”). In this example, the 2 steps displayed are given two different letters:

  • A = a critical to quality step that, if not executed as planned very consistently, will result in customer dissatisfaction.
  • C = a step that still needs to be controlled but less strictly.

Control Plan Excerpt

The ‘Critical to Quality’ Steps and CTQ Trees

CTQ trees are a good way to visualise the concept’s steps, demonstrating the breaking down of broader customer ‘needs’ into measurable attributes; with each ‘need’ having its own tree.

They have three branches: Need, driver/s, and requirement/s and leave you with a tangible list of requirements that must be met in order to offer a product or service that customers really want and like.

example critical to quality tree

Here are some examples of different branches of the CTQ tree that everyone can relate to:

Having a Nice Experience in a Café (CTQ Tree Example)

Need – To have a nice experience in a café – this is the voice of the customer.

Driver – This can be broken down into a number of different drivers such as ‘the speed of service’, ‘the quality of the food’, and ‘the price of food and drinks’

Requirements – These stem from the drivers, so for ‘the speed of service’ the requirements could be the customer wait time for both drinks and food, these would probably be different depending upon what the customer orders.

CTQ – These are the measurable attributes for each of the requirements which ensures the customer’s needs are met. The wait time for drinks, for example, could be set to less than 10 minutes.

Here is a completed CTQ Tree for this example:

cafe experience CTQ tree

How CTQ Works

CTQ takes the ‘voice of the customer’ and turns that into a set of attributes that drive the product design, allowing each attribute to be broken down into quantifiable actions. The customer’s need is split into specific drivers which in turn are broken down into measurable attributes.

CTQ has to be a measurable attribute as it is ultimately part of the product design that is either critical to the product performance or has the perceived quality associated by the customer.

The Voice of the Customer

To start with, you need to understand what the ‘voice of the customer’ is, AND define what is required for a product to satisfy the needs of a customer.
At the same time, you should be identifying which of these needs are classed as a ‘standard and expected’ vs. a ‘wow factor’. Let’s go into this, as it is an important distinction.

The ‘wow factor’ requirements are those that set you apart from your competitors. However, ensuring the ‘standard and expected’ requirements are 100% fulfiled is not an option – it is a must too.

The following diagram is a visual representation of customer expectations on product features:


ctq customer expectation change voice of the customer diagram ctq
As you can see in the diagram, the ‘innovative’ and ‘wow factor’ features migrate towards the ‘normal and expected’, from a customer expectation viewpoint. This means you always need to be thinking about ways to stay ahead of the competition and giving the customer more new and exciting features in the new products you are planning.

This diagram was developed by Professor Noriaki Kano in the 1980s as a theory for product development and customer satisfaction. It classifies customer preferences into five categories:

  • Must-be Quality – These are the standard and expected attributes
  • One-dimensional Quality – These attributes result in satisfaction when fulfilled and dissatisfaction when not fulfilled.
  • Attractive Quality – These attributes provide satisfaction when achieved fully, but do not cause dissatisfaction when not fulfilled
  • Indifferent Quality – These attributes refer to aspects that are neither good nor bad, and they do not result in either customer satisfaction or customer dissatisfaction.
  • Reverse Quality – These attributes refer to a high degree of achievement resulting in dissatisfaction and to the fact that not all customers are alike.

Source: https://en.wikipedia.org/wiki/Kano_model

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