What is a parameter in statistics?

A parameter in statistics refers specifically to a numerical characteristic that describes a population. This definition is crucial in distinguishing between a parameter and a statistic, which is the corresponding characteristic that describes a sample drawn from the population. Parameters provide valuable information about the entire group being studied, such as the population mean, population variance, or population proportion. Because parameters summarize the entire population, they are often unknown and estimated using statistics derived from samples.

The other options describe concepts that are related to sample data or specific calculations but do not accurately define a parameter. A characteristic describing a sample refers to statistics, not parameters. A measurement of sample variability pertains to how much the sample data fluctuate, which is again related to statistics. A constant used for statistical calculations generally describes theoretical constants or coefficients employed in various statistical formulae, rather than the concept of a parameter itself.