That's true, but that's also not a random sampling so doesn't really detract from what the above poster is saying. Most social science experiments do not initi

That's true, but that's also not a random sampling so doesn't really detract from what the above poster is saying. Most social science experiments do not initially handle random samples. The famous ones like the Milgram experiments and others conducted by the same researcher do. If I have my facts correct, he used to mail out letters to people randomly chosen from the phonebook to ask them to participate in his study, then travel to their locales to study them. The Milgram experiment itself was redone multiple times, using different population segments---students, random people in the city, all women, all men, etc. As an anecdote of how poorly correlated a social experiment can be to real life---in my university, econ & social science students were required to take at least 10 experiments per semester. Often we would go there, realize the material tested was identical to what we had studied in class then behave like 'rational market actors' in order to get the best result (econ experiments used small sums of real money, so you'd be paid at the end based on performance). This isn't anything like how a random person would have behaved.