How to Assess the NI Margin?

Prof. Mary Ferrill explains how to evaluate P values, power, and mainly the NI margin in this video.

When interpreting P values in NI, we have to keep in mind that if an NI study cannot show non-inferiority, this doesn’t mean the treatment is inferior. NI studies can only find NI or NOT.

When interpreting power in NI, we need to know that NI margins are generally smaller than the minimally important effect used to calculate power in superiority studies. Wider margins can lead to a type I error, while narrower margins can lead to a type II error.

Then we are given an example on NI power calculation. Pay attention to the NI Power Criteria.

As a reader, when we assess the NI margin, we need to make sure if the NI margin is appropriate and where did it come from. Besides, it should be clinically relevant and PRESTATED in methods selection.

Ultimately, we are given two examples. Would choosing a 12% margin rather than 10% be “easier” or more difficult to meet NI? Please share your thoughts and answers below.