I am working on a Design Verification project for a customer where the acceptance criteria used for a diameter feature is K-Factor Analysis at 90%/90% Confidence/Reliability (C/R). The idea is that at stated C/R values, once you compute your Tolerance Intervals, they should be within your specification limits (Upper-one sided limit in our case)

Out of 30 datapoint collected recently, 1 point is outside specification. However, the K-factor (or Tolerance Interval) is still within specification limit (as the process average is well within the USL and std. Deviation is very small).

Our team is suggesting that we can chose to ignore the fact that one point was outside specification since the K-factor is still within specification limits! Doesn't this violate the very first requirement to perform any statistical analysis, that is, the data has to be "in control" prior to analysis?

Has anyone else run into this situation? If so, how did you handle this predicament?

Thanks in advance for your help!