There are several factors that must be considered when determining the appropriate sample size including risks associated with the product, costs associated with producing the product, and costs associated with inspection, measuring, and testing. It is very important to consider the risks associated with the product. The Bayes Success-Run Theorem is one useful method that can be used to determine an appropriate risk-based sample size for process validations.

Now the point raised above that the statistical sampling is based not the confidence and reliability levels. This also depends on the risks associated with the product.