Seeking input on how to define limits for comparability testing. Challenge: Small number of pre-change lots.

Question

Hi,

I've dug through the forum and some other sites and am having some difficulty finding clear guidance.  Anything that the JMP community can offer here would be appreciated.

I need to do a comparability assessment on pre vs post change product lots (release data).  I'll be testing for Equivalence but am unsure of the best approach for defining equivalence margins for a few attributes.  There are only 4 pre-change lots.  I've seen different advice on using tolerance intervals vs. a 3SD approach.

What have people here done when in similar situations?  Any other approaches that I should consider?

Thanks in advance.

herush · Answer

Each comparability scenario requires different questions to be asked, most importantly will you be using an equivalence test or a quality range to establish comparability. The answer to that depends on the criticality of the evaluation and sample sizes. For quality ranges, it is typical to use a reference interval (mean +/- 3 standard deviations for example). There are lots of references for this. For equivalence testing, it will be more involved to determine your EACs. Here is a good paper that explains:

Feel free to reach out for clarification, thanks, Heath

MRB3855 · Answer

Hi @ClusterFerret68 : Defining equivalence limits can be very challenging.  Strictly speaking, it is not a calculation and it really isn't even a statistical issue; it is a scientific issue.

Here is a discussion you may find helpful.

https://community.jmp.com/t5/Discussions/calculate-the-Margin-of-Difference-for-the-TOST/m-p/845690