According to Pokémon Go Informer, if you want to evolve your Tyrogue into Hitmontop, your Tyrogue's highest IV stat has to be its Hit Points. If you want to evolve Tyrogue into Hitmonlee, the highest IV stat has to be Attack. If you want to a Hitmonchan, your Tyrogue's highest IV has to be Defense. You can check your Tyrogue's IVs by getting it appraised by your Team Leader in Pokémon Go, who will tell you the Pokémon's strongest stat. So if you want to get a Hitmontop, make sure your Tyrogue's highest IV stat is its HP.