This is from a thread with a similar complaint about the difficulty of ranking up due to interference from inters and bad players.
The math holds true for any set of assumptions, but if you'd like specific numbers put in I can do that for you.
Just tell me what you want your base win rate to be, the winrate of a team with a first timer, and the sample sizes desired.
[{quoted}](name=Silent Gravity,realm=NA,application-id=ZGEFLEUQ,discussion-id=4kEPNhj2,comment-id=000000000000,timestamp=2018-08-28T20:34:47.129+0000)
The matchmaking system relies on MMR.
The following uses the term "inter" but you can substitute AFKer, feeder (unintentional), high/drunk, bad at teamfights, bad at peeling, bad at counter jungling, tank focuser, or any
There are X inters at your MMR, and Y total players, then the probability of any slot being filled with an inter is X/Y.
Since you are never an inter, there are 4 slots on your team that can be inters, and 5 slots on the opponents team that can be inters.
Imagine 900 games with inters. Approximately 400 would have the inter on your team, and approximately 500 would have the inter on the other team. The outcome of those games will be heavily in favor of the team without the inter. I'm going to use a 99% winrate for the team without the inter. Other numbers can be substituted as you wish.
The number of games without inters has no effect of the outcome of these games. If it was 1 natural game (at 50% winrate assuming that you are at the exact average skill level for your MMR) and 900 games with interference from inters your expected outcome would be:
.5 wins from the 1 natural game (50% of 1)
4 wins from the inter being on your team (1% of 400)
495 wins from the inter being on the other team (99% of 500)
.5 losses from the 1 natural game (50% of 1)
396 losses from the inter being on your team (99% of 400)
5 losses from the inter being on the other team (1% of 500)
499.5 wins and 401.5 losses from 901 games. 55.4384% winrate
Again, but now with 9100 natural games (at 50% winrate assuming that you are at the exact average skill level for your MMR)
4550 wins from the 9100 natural games (50% of 9100)
4 wins from the inter being on your team (1% of 400)
495 wins from the inter being on the other team (99% of 500)
4550 losses from the 9100 natural games (50% of 9100)
396 losses from the inter being on your team (99% of 400)
5 losses from the inter being on the other team (1% of 500)
5049 wins and 4951 losses from 10000 games. 50.4900% winrate.
The winrate dropped by almost 5% when the inter games were less common (given the assumption of a 50% winrate for natural games).
If your natural winrate at the MMR you are currently at is less than 55.4444%, then inters existing in your games increases your winrate.
If your natural winrate at the MMR you are currently at is more than 55.4444%, then inters existing in your games decreases your winrate, but at that winrate you'll rank up fairly quickly anyway.
