I have a product with three active pharmaceutical ingredients. During data analysis of the assay (% content of the API) from 10 batches, two APIs out of three donot comply the process capability Index. The content of the API were 500 mg, 60 mg and 4 mg. The Cpk was more than 1.33 only in the API of 500 mg. However, all three were within the specification. The USL and LSL were respectively 110% and 90%. The maximum assay obtained was 107% which was responsible to cause high standard deviation, otherwise other were in the range of 100%.
Now my question is although the process capability index is less than 1.33, could we conclude that the process is suitable as all the parameter meets their specification?