What?

7797497
I mean what was the ETS criteria for turning someone into a night pony versus turning them into a unicorn.

7797583
Ets? Speak normal.

7797585
https://www.fimfiction.net/story/400051/pandemic-what-you-are-meant-to-be

7797589
This does not explain your original question. Again, speak normal.

7797605
I mean what made a person in the pandemic universe become a given type of pony.
(I'm writing this through a translator)

7797607
Sorry, I guess general ability, occupation, or even personality. I don't have a direct answer.

Let's give an example. John Smith is a construction worker, and is exposed to this pandemic. John is pretty good at his job, but it could be done by any race of pony.

If he was a pegasus, he might be bringing up material on a pulley system or have a good eye for inspection.
If he is an earth pony, he might be a general worker or on demolition jobs.

If he is a unicorn, he might be ensuring safety measures by setting up magical protection or clearing material with their magic.

Does this give you a good idea?

7797615
from what i remember it was mostly about personality and i know in one of the stories it was said what was the main factor of turning into a night pony.

7797615

7797617
It is a complex system, and the original ETS spell also had other spells attached that acted to maintain quotas so tribes would be distributed in certain numbers. Each tribe had mental things that it was looking for, but depending on where the percentage quota was at the time it might not sort a person into the ideal tribe if there were too many as a percentage of that tribe already, in which case it would default to earth pony.

There is no singular thing for any tribe to be selected on. As each was chosen based on a variety of factors Some features for choosing might be used for multiple tribes (athleticism for both pegasi and earth ponies, loving to fly for both pegasi and night ponies). Primarily, it was sorting people into the tribe it felt they fit in best with, within the parameters of the quotas. There were a lot of people that ended up earth ponies that might have fit well with one of the other tribes, but the quotas kept them out.

There are other factors like the fact Sunset Shimmer overcompensated for females in the night pony tribe because she assumed that the traits ideal for night ponies that she had chosen for would be so prominent in males it would make it so there were hardly any female night ponies (she poorly judged human females and the opposite ended up happening instead).

Crystal ponies were not part of the design, and it is unknown if there were particular traits that they were chosen for.