What is the normal range for Match making?

When playing ranked I see a huge range of players. I'm gold 4 right now (I know low ranked garbage who can't have any opinions because I'm bad) and I see anywhere from gold 1 to silver 2. I know the mmr system on op.gg is flawed but according to them I played with people having silver 4 mmr and plat 5 mmr, is that normal? My mmr was normal for my rank so is having such huge swings normal? This isn't meant to be flaming the match making system I'm just curious how wide of a net they cast for Match making.