During my experience, I have noticed that most companies have Validation Engineer that performs various tests to validate a machine which is also known as (IQ, OQ, & PQ). There are some specific guidelines set by the FDA that aide the Validation Engineer when carrying out the tests. Furthermore, there are different kinds of validations such as design validation, software validation, machine validation etc. that requires different method. Usually, validation engineer tries to takes the worst case possible to make sure the process is repeatable and documents the objective evidence. All in all, I agree with the above posts and the lecture notes on verification and validation.