Sampling is the selection of a given number of units of analysis (people, households, firms, etc.), called cases, from a population of interest. Generally, the sample size (n) is chosen in order to reproduce, on a small scale, some characteristics of the whole population (N)

Sampling is a key issue in social research designs. The advantages of sampling are evident: feasibility of the research, lower costs, economy of time, and better organization of the work. But there is an important problem to deal with: that is, sampling error, because a sample is a model of reality (like a map, a doll, or an MP3) and not the reality itself. The sampling error measures this inevitable distance of the model from reality. Obviously, the less it is, ...