The fishbone or Ishikawa diagram is one way to show cause-effects (a.k.a., root cause analysis-RCA). Another method uses a cause-effect Matrix.

Cause Effect Matrix in Excel

Process

1. Identify the key process outputs, requirements or effects. These are also known as critical to quality (CTQs).
   Optional: Add Upper and Lower Specification Limits (USL/LSL) and target to each output.
2. Use a weighting factor (e.g., 1-5) to identify the importance of each output to the customer.
3. For each process step, identify the key process inputs (i.e., causes).
4. Then use a weighting factor (e.g., 1-low, 3-medium, 9-high) to show the impact or correlation of the input (cause) on each output (effect).
5. The resulting total impact will be shown in the far right column and the ranking/priority of each input.

The Cause-Effect Matrix isjust one of the tools included in the QI Macros for Excel SPC Software for Excel.

Download the FREE 30-day Evaluation copy of the QI Macros Excel SPC Software for Six Sigma