topic Re: Tolerance intervals method in Discussions

Tolerance intervals method

SengYew — Wed, 04 Dec 2024 03:27:19 GMT

Dear sir/Madam,
As we know that is only have two available methods are Assume Normal Distribution and Nonparametric from tolerance intervals module, If I have 30 samples data that using Fitted Weibull/lognormal distribution and the P-value is >0.05. How do we using Tolerance interval for Weibull and lognormal distribution?

Re: Tolerance intervals method

MRB3855 — Wed, 04 Dec 2024 11:16:05 GMT

Hi @SengYew : If your data are Lognormal, then the natural log of the data will be normally distributed.

1. If X is your data, calculate Y=ln(X): Y has a normal distribution.

2. Get the desired Normal Tolerance Interval for Y.

3. Back transform the interval ( exp[lower TI], exp[upper TI] ) to get the Tolerance interval back on the original X scale.

Weibull? Not so straightforward I'm afraid:

See the following: Lawless, J. F. (1975). Construction of tolerance bounds for the extreme-value and the Weibull distribution. Technometrics, 17, 255—261.

Re: Tolerance intervals method

scappuccio — Tue, 17 Dec 2024 18:29:02 GMT

Hi @MRB3855,

Based on your above response I am assuming the answer is no - does JMP have integrated tools for construction of Weibull tolerance intervals per the paper you have referenced?

Re: Tolerance intervals method

MRB3855 — Wed, 18 Dec 2024 06:24:51 GMT

Hi @scappuccio You assume correctly; the answer is no. However, I don’t know if there are plans to add that functionality in the future.