Cusum Chart in Excel
Cusum Charts (Cumulative Sum Charts) are Used to Detect Smaller Shifts in a Process
The Cusum chart can detect process shifts more rapidly than the XmR or XbarR. If a trend develops, it's evidence that the process has shifted.
A Cusum Chart consists of the following:
- A target which is either provided by you or calculated as the mean of your data.
- Upper Cusum Limit and Lower Control Limit lines.
- C+ and C- lines which represent the cumulative sum of deviations of successive sample means from a target. Use these lines to determine if your process is shifting.
Here is a sample of a Cusum Chart created using the QI Macros SPC Software for Excel: