Sampling refers to the investigation of a part of the whole population or universe. A sampling procedure is a technique of selecting a sample from a given population. A statistical sample, according to Calvin, is a miniature picture or cross-section of the entire group or aggregate from which the sample is taken. ‘ The entire group from which a sample is chosen is known as the “population”, “Universe”, or” supply”.

In short, sample represents the whole population and by observing the sample, certain inferences may be made about the population. For collecting representative data, samples are not selected haphazardly but a proper procedure is adopted, so that the influence of chance and probability can be estimated.