Isaacs-Navarro conjecture

The Isaacs-Navarro conjecture is a slight generalization of the McKay conjecture and is believed to hold for all finite groups.

Statement
Suppose $$G$$ is a finite group and $$p$$ is a prime number. Denote by $$f(G,p,a)$$ the number of equivalence classes of irreducible representations of $$G$$ over the complex numbers whose degree is congruent to $$a$$ or $$-a$$ modulo $$p$$. Then, if $$a$$ is not divisible by $$p$$, and $$P$$ is a $$p$$-Sylow subgroup of $$G$$, we have:

$$\! f(G,p,a) = f(N_G(P),p,a)$$