Thank you, Michael. I did find the passage to which you are referring. I am actually looking for the math that is used, which is not in the provided link. Is there an article or book you can refer me to?
I think this paper might help:
Crow, L. H., (1982), “Confidence Interval Procedures for the Weibull Process with Applications to Reliability Growth,” Technometrics, Feb. 1982, 24:1, 67-72.