The population in a statistical research is the whole human group of interest, from which a sample would be taken with the aim of making feasible the data treatment. Moreover, inference takes place when certain methods are applied in order to reach conclusions from the data of the sample that can be generalized to the entire population.
In the example described above, the population are all US citizens with legal voting rights. All the individuals who met this conditions would be eligible for the sample. As a random sampling in conducted inside each of the states, a proportional sampling method is being applied in this research.
