Chapter 4: Statistical Process Control (SPC) - Control Charts (X-bar, R chart, c-chart, p-chart)
Abstract : In Statistical Process Control (SPC), a "control chart" is a graphical tool used to monitor a process over time, with the most common types being the X-bar chart (for average values), R chart (for range), c-chart (for count of defects per unit), and p-chart (for proportion of defective items), each helping to identify potential issues in a process by visually displaying data points against calculated upper and lower control limits, indicating whether the process is "in control" or experiencing significant variation requiring investigation. Key points about each chart: X-bar chart: Tracks the average value of a variable measured in a sample (e.g., average weight of products). Used to detect shifts in the process mean over time. R chart: Monitors the range (difference between the highest and lowest values) within a sample. Used to identify changes in process variability. C-chart: Counts the number of defects per unit or sample. Us...