What are the circumstances that make sampling unnecessary? Why are those circumstances rare?

Question

What will be an ideal response?

Answer 1

Sampling is unnecessary if all the units in the population are identical. Physicists do not need to select a representative sample of atomic particles to learn about basic physical processes. They can study a single atomic particle because it is identical to every other particle of its type. Similarly, biologists do not need to sample a particular type of plant to determine whether a given chemical has toxic effects on it. The idea is, “If you’ve seen one, you’ve seen ‘em all.”
A representative sample is a sample that looks similar to the population from which it was selected in all respects that are potentially relevant to the study. The distribution of characteristics among the elements of a representative sample is the same as the distribution of those characteristics among the total population. In an unrepresentative sample, some characteristics are overrepresented or underrepresented.
What about people? Certainly all people are not identical—nor are animals, in many respects. Nonetheless, if we are studying physical or psychological processes that are the same among all people, sampling is not needed to achieve generalizable findings. Various types of psychologists, including social psychologists, often conduct experiments on college students to learn about processes that they think are identical for all individuals. They believe that most people will have the same reactions as the college students if they experience the same experimental conditions. Field researchers who observe group processes in a small community sometimes make the same assumption.
There is a potential problem with this assumption, however. There is no way to know whether the processes being studied are identical for all people. In fact, experiments can give different results depending on the type of people studied or the conditions for the experiment. Milgram’s (1965) experiments on obedience to authority (discussed in Chapter 3) illustrate this point very well. Recall that Milgram concluded that people are very obedient to authority. But were these results generalizable to all men, to men in the United States, or to men in New Haven? We can have confidence in these findings because similar results were obtained in many replications of the Milgram experiments when the experimental conditions and subjects were similar to those studied by Milgram.
Accurately generalizing the results of experiments and of participant observation is risky because such research often studies a small number of people who do not represent a particular population. Researchers may put aside concerns about generalizability when they observe the social dynamics of specific clubs or college dorms or a controlled experiment that tests the effect of, say, a violent movie on feelings for others. Nonetheless, we should still be cautious about generalizing the results of such studies.
The important point is that social scientists rarely can skirt the problem of demonstrating the generalizability of their findings. If a small sample has been studied in an experiment or field research project, the study should be replicated in different settings or, preferably, with a representative sample of the population for which the generalizations are sought.
The people in our social world are just too diverse to be considered identical units. Social psychological experiments and small field studies have produced good social science, but they need to be replicated in other settings with other subjects to claim any generalizability. Even when we believe that we have uncovered basic social processes in a laboratory experiment or field observation, we must seek confirmation in other samples and other research.