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This is the situation I have. I am doing design verification and validation sampling. The validation requires three runs of the process to prove effectiveness of the changes. The process is run and I get the same number of samples for each run.

The sampling plan is set up for each run. There are different levels of confidence I can choose. For example 20%, 50%, or 90%.

Lets say I choose the 50% confidence per run. I know that after the first run I will have 50% confidence that the process is producing defects at or below the AQL. What will be my confidence after the second and third runs?

I have been told that confidence does not double with a second run. Is there a formula to calculate what it would be?

Thanks for any help you can give to me in figuring out how the confidence increases with multiple runs of a process.