iSixSigma

Critical to Quality (CTQ)

Definition of Critical to Quality (CTQ):

The kitchen manager looks over the list of equipment that will be needed for the new kitchen to be set up. The manager then tells the owner, “Well, I know that some of this equipment will be needed regardless of what you are serving to your customers, but the rest will definitely be impacted by your decisions as to your menu, and the level of quality you are trying to establish.” 

The kitchen manager continues his questions, asking: Do you see speed as a prime requirement? Quality of ingredients and method of preparation will also impact the required equipment list. Also, the breath of your menu will impact the different types of equipment and quantity of equipment we need to install. 

So, what are you trying to set up here with your new restaurant? What requirements will be critical to quality?

An overview: What is critical to quality?

Critical to quality, also known by the acronym CTQ, are the key attributes of a product or service that your customers have defined as being important. These measurable characteristics are what helps us understand what steps in our process are value-added, as these critical to quality characteristics help define the value.

To understand value-added and non-value added, we must first understand what the customer values, so we need to identify and prioritize who our customers are, and collect the VOC, or voice of the customer data. Using this data, we then determine the list of CTQ requirements.

A common tool used to prioritize a specific requirement is called a CTQ tree. This tool helps take customer requirements, which often start off broad, and turn them into performance requirements that can be measured.

In the example of kitchen equipment, the menu the owner is trying to establish, as well as the level of quality of the food, will directly impact the kitchen equipment required. So, if this was a fine dining establishment that served crème brule, the kitchen would require a brulee torch for the hardening of the top of the dish. If the restaurant is a burger joint, a brulee torch would likely be useless. 

The kitchen manager must understand the customer needs before setting up a kitchen that can meet those needs. Maybe they are making hundreds of crème brulee a day, for delivery to local shops, so a traditional crème brulee torch would not be practical, and some automatic machine that can harden the tops of thousands of crème brulee a day is required. 

All the characteristics from the customer are needed to establish what is critical to quality.

A CTQ for the making of the crème brulee might look like the example below:

An example CTQ tree for making creme brûlée at a restaurant

The CTQ tree helps take the initial customer desires and turn them into measurable deliverables.

3 benefits of attending to CTQ

Before you feel tempted to shrug off this step, deeming it unnecessary, consider a few key ways it can benefit you to consider what is critical to quality.

Making it possible to understand and meet your customer’s needs

If you don’t know the characteristics that make up your customer’s products or services, how can you be expected to make your customer happy on a regular basis? Knowing the CTQ information makes it possible to understand value, eliminate non-value-added activities, and satisfy your customer.

Less rework

When you do not understand the CTQ, you are bound to fail to meet your customers’ requirements, and thus your process will require rework. When you’ve established the metrics using your CTQ trees, you can spot your quality errors sooner, decreasing the cost of rework.

Saves time

Less rework also means less time spent performing the rework and less time trying spent apologizing to the customer regarding errors.

3 CTQ best practices

  • Collect as much data regarding the CTQ as possible. It’s easy to overlook key customer requirements.
  • Ask the customer the same questions, but in different ways. You will often find that a reworded question will get you a slightly different response that may shed additional light on a hidden requirement.
  • Remember to use your CTQ trees to help you develop your metrics. Quality is maintained through the metrics you set up, both for verifying that customer demands are being met and for identifying errors as soon as possible.

Frequently Asked Questions (FAQ) about CTQ

How deep do I need to dive when doing the CTQ tree?

Usually, the deeper the better, as the customer will not always understand what they are asking for until they realize they forgot to ask for an important feature. 

Going back to the example CTQ tree, the requirement on the mechanical lowering of the beater blades into the mixing bowl did not state how far into the bowls the beaters have to descend. If the beaters only lower two inches into the bowl, they may not mix the custard well enough. Going back and asking for a measurement would be advisable. Other requirements, such as how “oval” does the oval dishes need to be, may not be a critical factor. 

How do I tell a key CTQ characteristic from a lesser important CTQ characteristic?

It can be a challenge to separate a nice-to-have feature from a critical necessary characteristic. It can be helpful to use your information from the VOC, or Voice of the Customer, to help determine criticality for each element.

Are there any other tools that can assist with setting up CTQ?

One tool worth considering is the quality function deployment (QFD) tool. This is a methodology that assists with transferring information from the VOC and transforming it into CTQ, including assigning priority actions required to meet key attributes.

Critical to quality is necessary to meet customer expectations

Critical to quality describes the key characteristics needed to meet customer demands. These should be measurable factors, developed from the Voice of the Customer exercises. It is important to collect as much data as possible from the customer, then transform that data into key deliverables. 

By measuring the key metrics, you can be sure to spot errors earlier in the process and make your customer happy by meeting their expectations.

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