Estimation is the process of providing a numerical value for an unknown quantity based on information collected from a sample. If a single value is calculated for the unknown quantity, the process is called point estimation. If an interval is calculated that is likely, in some sense, to contain the quantity, then the procedure is called interval estimation, and the interval is referred to as a confidence interval. Estimation is thus the statistical term for an everyday activity: making an educated guess about a quantity that is unknown based on known information. The unknown quantities, which are called parameters, may be familiar population quantities such as the population mean μ, population variance σ2, and population proportion π. For instance, a researcher may be interested in ...