After reading this answer, I found myself confused. Say I am looking for the percentage of people who are likely to vote for a particular candidate. I am sampling from a population which is known to have groups with non-independent answers, for example, a family (such as husband and wife who gives exactly same answers). Hence, I can expect my sample to contain some of these groups too. Now, in a strict sense, can I use random sampling here to obtain the percentage of votes expected?
I understand sampling is routinely used, but is it usable in a strict theoretical sense? Or are we only taking about the independence of the sampling process alone, and not the population?