Does switching out effect the amount of evs gained?

Yes, switching out a Pokémon during battle does affect the amount of EVs (Effort Values) gained. When a Pokémon faints an opponent, the Pokémon that participated in the battle will receive the EVs associated with that defeated opponent. However, if a Pokémon is switched out before the opponent is defeated, it will not receive any EVs from that battle, regardless of how much damage it inflicted.