The statistics of the PTI test is based on normal distribution. We have a database collected that demonstrates that this assumption of normality is appropriate. To challenge the test, though, we have studied a number of non-normal distributions and recently non-normal distributions that have been suggested by the agency to be very challenging non-normal distributions.
Our investigations have revealed that with the revised PTI test coefficients, the PTI test assures less than 5.1 percent type I error at the limiting quality for all normal and for most non-normal situations. For a few extreme distributions, 5 percent is exceeded at the limiting quality. These extreme distributions are not reflective of real products. They are significantly off-target, relatively symmetric distributions with extremely short tails or they could also be significantly off-target, notably asymmetric distributions with the longer tail in the off-target direction. Now, we conclude that the PTI test is appropriate for real products.
Zero tolerance has also been a criterion, mostly because it's part of the present guideline test. It has been under consideration whether or not the