Well the 5% is averaged over the whole group while the 300% is from a base rate of those who go to college. I haven't seen the data, so I don't know if this is

Well the 5% is averaged over the whole group while the 300% is from a base rate of those who go to college. I haven't seen the data, so I don't know if this is the case, but one explanation is that this intervention works really well for some people, and not at all for others. Also, I think "3x more likely" means 200% more people. So the numbers could be something like: 100 participants, 5 would have gone to college. The social stimulation really benefited 10 kids. They, in turn, did years more schooling and went to college. 5% -> 15% college rate is 3x more likely, but the 10 kids' large increase in attendance was averaged out over the group of 100, so the overall increase was just 5%. Not saying this is the case, just showing a way those numbers could be plausible.