I’m not sure what’s being asked.
3 out of 4 would make up 75% of the population as long as you know for sure they are talking about all people in all parts of the sentence.
For instance, with the COVID vaccination rate you need to know if they are quoting eligible population or total population.
Another trick is if it says 3 out of 4 dentists asked say Crest toothpaste is best. That’s only those asked not the total population of dentists.
Or, 3 out of 4 dentists say Crest toothpaste fights cavaties. That sentence doesn’t exclude other toothpastes as fighting cavaties just as well.