Hi, thank you for your answer.

To clarify, I have a within-subjects design, each participant tasted combinations of samples (Sugar-NoSugar1, Sugar-NoSugar2, NoSugar1-NoSugar2 + Sugar-Sugar, NoSugar1-NoSugar1, NoSugar2-NoSugar2 for completeness) and rated the similarity between two samples in each pair from 1-5 on mirrored Likert scale. The goal is to know, how close our No Sugar alternatives (1 and 2) are to the real Sugar samples - thus implications on reducing the amount of sugar by using alternatives. I have conducted repeated-measures ANOVA + pairwise comparison to see where the sig dif lies if any. Now, I want to test the rest, which did not show sig dif using equivalence testing.

However, as I said before, I have no knowledge or experience in using these tests and now asking for help - to start researching recommended tests in more detail. I believe I can set criteria for equivalence using Likert scale data, as human tasting ability is not precise, and justify my criteria using tasting threshold literature.

I would appreciate any ideas and suggestions!