A parameter is the value that is obtained from (1) population (2) sample of scores and is employed to explain the population. A statistic is a value obtained from sample and is employed to explain the (1) population (2) sample. Typically it is impossible to obtain measurements for an overall population, so researchers should rely on information from samples; that is, researchers employ statistics to obtain information about unknown parameters. However, samples provide only limited information about their populations. Thus, sample statistics are usually not identical to their corresponding population parameters. The error or discrepancy between a statistic and the corresponding parameter is called sampling error.