what is the reference that supports - Control charts are statistical process control tools used to assess whether a manufacturing or business process is in a state of control. They are also referred to as Shewhart charts or process-behavior charts. 1. Purpose of Control Charts: - Track Process Variation: Over time, control charts can be used to track a process's variation and central tendency. - Identify Out-of-Control Signals: These aid in locating any circumstances that render a process out of control. - Evaluate Process Stability: They are employed to evaluate a process's stability. - Predict Future Performance: They can be used to forecast how well a process will perform in the future. 2. Causes of a Process Being Out of Control: - Special Cause Variation: This type of variation results from particular circumstances rather than being a process inherent feature. Examples include malfunctioning machinery, inexperienced workers, or a supplier change. - Variation with a common cause is one that is a natural byproduct of the process. It is the outcome of the process's management and design. 3. Correcting an Out-of-Control Process: - Determine the Cause: Finding the variation's cause is the first step. Root cause analysis could be used for