What is QC?

QC stands for Quality Control. But is control truly being practiced? In my experience, many companies simply repeat checking activities. If that’s the case, shouldn’t we call it Quality Check instead? Why do we call it Quality Control? This is the first question to consider.

What exactly is control? Control refers to the activity of returning a process that is deviating or has deviated from the standard back to that standard.

To explain this in simple terms, consider the example of baseball. In baseball, when a pitcher aims for the strike zone to throw the ball, this is called control. QC means controlling the process to aim for the quality strike zone.

Where exactly is this quality strike zone documented? The quality control, or the quality strike zone, is described in the SOP (Standard Operating Procedure).

Here, there is something important to note. While Japanese uses the single word “管理” (kanri), English distinguishes between two concepts: Control and Management.

The difference is that Management corresponds to the manager in baseball, while Control corresponds to the pitcher. Management involves department heads and section managers at the managerial level observing the current situation and giving instructions. On the other hand, frontline workers control their own work according to the SOP while aiming for the strike zone—this corresponds to QC (Control). In other words, everyone is in the position of the pitcher.

The quality standard (strike zone) is documented in the Standard Operating Procedure (SOP) or, in the case of GMP (Good Manufacturing Practice) manufacturing facilities such as pharmaceutical plants, in the product specification document. Controlling work to aim for that strike zone is Quality Control.

Let me explain with an example. Suppose you outsource data entry of 1,000 items to an external vendor. In the contract, you agreed to accept delivery if errors are within 0.3%. When you receive the completed data and begin checking, you find 1, 2, 3, 4 errors.

If this exceeds the 0.3% error rate stipulated in the contract, you say, “This delivery exceeds the 0.3% error rate, so we cannot accept it,” and return it to the vendor.

There is something crucial here. You must not tell them where the errors were. This is because if you point out the error locations, the vendor will simply correct only those indicated errors and resubmit. This would then require you to check the remainder again.

Furthermore, you must not tell them how many errors there were. If you communicate the number, they will likely correct only that many errors and resubmit. Again, this would necessitate checking for remaining errors.

This is not a good situation. When subsequent processes involve people in later stages checking data on behalf of the responsible party and even making corrections, you fall into the dilemma of never improving data quality.

This is extremely important. What QC requires is not just checking, but properly returning work that doesn’t meet standards. The fact that careless work or poor-quality work will be rejected serves as a deterrent. As a result, the responsible party becomes more focused on data quality control and quality assurance.

Please don’t misunderstand—I’m not saying that checking is not QC. Rather, checking alone does not constitute QC. There must be proper control.

As in the example above, for items that deviate from the standard, Quality Control means returning them to the process and not allowing them to proceed to the next process until they meet the standard. This is an extremely important process.

Let me give another example. Suppose a cookie factory’s manufacturing instruction sheet states that cookies should be baked at 170°C ± 5°C. The person in charge of the burner reduces the heat when the temperature is about to exceed 175°C and increases the heat when it’s about to fall below 165°C.

This is because exceeding 175°C will burn the cookies, while falling below 165°C will leave them undercooked. In other words, by baking within the temperature range of 170°C ± 5°C as stated in the instruction sheet, the predetermined delicious cookies are produced.

This is Quality Control. In other words, if work is performed according to the SOP, products should necessarily be manufactured with the predetermined specifications and predetermined quality. If the product quality still fails to meet specifications or the service cannot be provided properly despite following procedures, it means the SOP is incorrect or the standard is wrong.

Understanding Control vs. Management in Quality Systems

Aspect	Control	Management
Baseball analogy	Pitcher	Manager/Coach
Who performs it	Frontline workers, operators	Department heads, section managers
Primary activity	Execute work according to SOP, maintain process within standards	Observe current situation, give instructions, make decisions
Focus	Operational execution, real-time adjustments	Strategic oversight, resource allocation
Relationship to standards	Direct implementation of standards	Setting and reviewing standards

Key Principles of Effective Quality Control

Quality Control is fundamentally about maintaining process stability within defined parameters. The effectiveness of QC depends on several critical factors:

Clear Standards: Standards must be documented in SOPs with specific, measurable criteria. Ambiguous standards cannot be controlled effectively.

Real-time Monitoring: Like the baker monitoring oven temperature, operators must continuously observe process parameters and recognize when intervention is needed.

Corrective Action Authority: Frontline workers must have the authority and responsibility to take corrective action when processes begin to deviate from standards, without waiting for management approval for routine adjustments.

Feedback Loops: When non-conforming work is rejected, it creates a natural feedback mechanism that encourages upstream process improvement. This is why simply identifying and correcting errors downstream is insufficient—the responsible party must feel the consequences of poor quality.

Distinction from Inspection: While inspection (checking) identifies non-conformance, control involves both detection and corrective action to return the process to standard. Inspection without authority to reject or return work is merely quality checking, not quality control.

The discipline of returning substandard work rather than fixing it downstream may seem inefficient in the short term, but it is essential for long-term quality improvement. It places responsibility where it belongs—with the person or process that creates the output—and creates the motivation for sustained quality performance.

When properly implemented, Quality Control ensures that each process step delivers output that meets defined standards before proceeding to the next step, creating a robust chain of quality throughout the entire operation.