Here are the key steps to conduct a variable MSA:
1. Select a part/product with known measurements.
2. Select operators who will use the measurement system.
3. Have operators measure the part multiple times.
4. Analyze the data using one of the methods:
- Bias study to determine if the measurement system is accurate.
- Linearity study to determine if measurements are proportional to actual size.
- Stability study to determine if measurements drift over time.
- Repeatability & reproducibility study to determine precision between and within operators.
5. Compare results to customer specifications for capability. Ensure Cp, Cpk are greater than 1.33.