Based on what the sample size to do MSA?

There are different types and purposes of MSA studies. One of them is GRR, which is a repeatability and reproducibility study. In this study, 3 operators measure 10 parts three times.  In other words, MSA study is performed according to 90 measurement results.

Another example of MSA studies is "BIAS" study.

The meaning of BIAS is the difference between the observed average of measurements and the reference value.  In this study, the reference part is measured at least 10 times by an operator.

As I mentioned above, there are different types of MSA studies. Such studies are applied according to the type of device and purpose.

For more information, you can see the following article:

• How to Establish Measurement System Analysis According to IATF 16949 https://advisera.com/16949academy/blog/2017/11/08/how-to-establish-measurement-system-analysis-according-to-iatf-16949/