Which of the following is not found on an X-bar and R control chart?

Which of the following is not found on an X-bar and R control chart?

• A. Average
• B. Range
• C. Standard deviation
• D. Capability ratio

Answer: (D)

An X-bar and R control chart primarily focuses on monitoring the mean and variation of a process over time. The X-bar chart displays the average values of a sample set, which allows analysts to track how the process mean changes. The R chart, on the other hand, represents the range of variability within each sample, capturing the difference between the largest and smallest values. The capability ratio, while relevant in quality control, is not a parameter that is directly plotted on X-bar and R charts. This ratio typically indicates how much a process can meet specifications, often represented through metrics like Cp or Cpk. Its calculation relies on information derived from the control charts but is not itself a component illustrated within the charts. This distinction clarifies why the capability ratio is not represented on X-bar and R charts, differentiating it from the average and range, which are fundamental to these control tools in statistical quality control.

An X-bar and R control chart primarily focuses on monitoring the mean and variation of a process over time. The X-bar chart displays the average values of a sample set, which allows analysts to track how the process mean changes. The R chart, on the other hand, represents the range of variability within each sample, capturing the difference between the largest and smallest values.

The capability ratio, while relevant in quality control, is not a parameter that is directly plotted on X-bar and R charts. This ratio typically indicates how much a process can meet specifications, often represented through metrics like Cp or Cpk. Its calculation relies on information derived from the control charts but is not itself a component illustrated within the charts.

This distinction clarifies why the capability ratio is not represented on X-bar and R charts, differentiating it from the average and range, which are fundamental to these control tools in statistical quality control.