# Significance testing difference in two changes of NPS. Significance of difference, NOT NPS itself.

I'm trying to calculate if the difference between two NPS changes is significant.

For clarity: I have groups $$a$$ and $$b$$; group $$a$$'s NPS increased by $$20$$, group $$b$$'s NPS increased by $$10$$, so the change for group $$a$$ in comparison to group $$b$$ is $$10$$. I want to check if the difference of the differences is significant, not just the change in NPS for group $$a$$ and group $$b$$.

I'm asking as I have used a different significance test for NPS in the past, and wondered how you can apply that (or if you need to apply that) to this.

Thanks!