for example, let's say there is a policy that randomly allocated immigrants to every municipality of a country, and I am interested in the effect of increased immigrant population on voting outcomes. I can observe every voting outcome in the municipality, so in a sense, I have the entire population. why do I have standard errors? why is this a 'draw' from the population? is the idea that if I were to go back and do it again, it could be the case that something different could have happened if we went back in time and did it again, so the 'true' effect is still out there?