Certified Production & Operations Manager (POM) Practice Exam

What are the two main causes of variation in statistical control?

1. Natural causes and assignable causes

2. Random causes and predictable causes

3. Systematic causes and chance causes

4. Environmental causes and human causes

The correct answer is: Natural causes and assignable causes

The concept of variation in statistical control is pivotal in quality management and process control. The correct answer identifies the two primary sources of variation: natural causes and assignable causes. Natural causes, often referred to as common causes, are inherent variations within a system. These are typically random and expected fluctuations that occur in any process over time. They are part of the system's normal functioning and are generally caused by minor, difficult-to-identify factors that can affect the outcome. Since these variations are predictable and stable, they do not indicate a problem with the process. Assignable causes, on the other hand, are variations that arise from specific, identifiable factors. These variations are not inherent to the process and can be traced back to specific causes, such as equipment malfunctions, human errors, or changes in raw materials. Recognizing assignable causes is crucial because they point to areas for improvement or corrective actions, allowing managers to enhance the process to reduce defects or inefficiencies. By distinguishing between these two types of variations, organizations can implement appropriate control strategies. For example, they may focus on reducing common causes through process improvements or address specific assignable causes promptly to maintain the overall quality and performance of their processes. The other options, while they suggest different factors that