Question 66

Common cause of variation is considered a random cause that cannot be identified.

Common causes of variation are inherent to a process and cannot be traced back to a specific identifiable source. They represent the natural variability that occurs within a system, making it difficult to pinpoint their origins.

A) Assignable cause of variation

Assignable causes of variation are identifiable and specific factors that can be traced back to a distinct source, such as equipment malfunction or operator error. Since they are not random and can be controlled or eliminated, they do not fit the definition of a random cause that cannot be identified.

B) Structural variation

Structural variation refers to differences caused by the physical structure or setup of a system. While it can contribute to variability, it is not considered a random cause in the same way as common causes, as it can often be linked to identifiable factors in the system's design.

C) Common cause of variation

Common causes of variation are indeed random and cannot be traced back to specific identifiable sources. They are inherent to the process and are typically the result of multiple factors that contribute to the natural variability observed in a system.

D) Tampering

Tampering refers to inappropriate or unnecessary adjustments made to a process in response to variability. This is not a cause of variation in itself; rather, it can exacerbate existing issues. Tampering is also identifiable and not considered a random cause.

Conclusion

The identification of common causes of variation as random highlights their inherent nature within processes, making them difficult to isolate or eliminate. In contrast, assignable causes and tampering represent identifiable factors that can be managed. Thus, common causes stand out as the only option that aligns with the definition of a random cause that cannot be identified.