If 100 mobs spawn during the night, how many of them on average will be endermen?
Enderman are very rare in the Overworld. Most people would agree that 1-2 would be a good estimate, but I conducted an experiment where I would create a random world, wait until nighttime, and count the mobs that spawn.
The results vary:
On the first try, I found 1 enderman and 99 other mobs
On the second try, though, this number had spiked up to 4
On the third try, I got 3 enderman and 97 other mobs
On the fourth, surprisingly, I found 6.
I can't figure out the exact numbers, but the best guess would be that out of 100 mobs that spawn during nighttime, 3-5 of them will be Endermen.
Hope I helped...