Pub. date: 2007 | Online Pub. Date: September 15, 2007 | DOI: 10.4135/9781412952651 | Print ISBN: 9781412924702 | Online ISBN: 9781412952651| Publisher:SAGE Publications, Inc.About this encyclopedia
Joseph M. Whitmeyer
For describing or testing hypotheses about a population, sampling a small portion of the population is often preferable to taking a census of the entire population. Taking a sample is usually less expensive and less time-consuming than taking a census and more accurate because more effort and care can be spent ensuring that the right data are gathered in the right way. Data collected appropriately can be used to make inferences about the entire population. Sampling techniques can be categorized into nonprobability samples and probability samples. A probability sample is selected in a way such that virtually all members of a population have a nonzero probability of being included, and that probability is known or calculable. A nonprobability sample is gathered in a way that does not depend on chance. This means that it is difficult or impossible to estimate the probability that a particular unit of the population In ...