What is the MMR balance per member of a premade?

Seriously, we may overall be similar team MMR averages as 5 solos vs a team with a premade, but we have already a lesser chance of winning because of the premade. Solos vs premade should have the averages be way more in favor of the solos since they dont have the synergy (and possible communication softwares running) that premades usually have.

Also, that average usually ends up being one player who is either massively lower or (more often than not) higher than the other 4's MMR levels to act as a counterbalance. 1 silver 2 does not make up for 4 bronze players when facing a team made up of some combination of silver 4's, 3's and 2's and with that one player who is unranked or low bronze to lower the team's MMR average, but is still grouped with some of the others so their lackings are sorta made up for, with intrest.