What are the two types of variance seen in control charts?

Here are the answers to your questions:

13. What are the two types of variance seen in control charts?
The two types of variance seen in control charts are:

• Common cause variation (also known as natural or random variation), which is inherent to the process.
• Special cause variation (also known as assignable cause variation), which arises from specific, identifiable factors outside the normal process.

14. How would you improve natural cause variation?
Improving natural cause variation (common cause variation) requires fundamental changes to the process itself. This involves redesigning the process, upgrading equipment, improving materials, or enhancing training, rather than addressing individual data points.

15. Would you try and improve the process if the R chart shows an out of control process?
Yes, absolutely. If the R chart (or S chart) shows an out-of-control process, it indicates that the process variability is unstable. This instability must be addressed and brought into control before attempting to interpret the X-bar chart or make improvements to the process average.

16. What are some common causes of variation in a production run?
Some common causes of variation in a production run include:

• Slight variations in raw material properties.
• Minor fluctuations in machine performance due to wear or environmental factors.
• Small differences in operator technique or fatigue.
• Changes in the environment such as temperature or humidity.
• Inconsistencies in measurement systems.

17. In what order must the data for a control chart be captured in?
The data for a control chart must be captured in chronological order (time sequence). This is essential for accurately detecting trends, shifts, and patterns in the process over time.