Estimation is approximate or uncertain calculation of a result, often based on approximate, uncertain, incomplete, or noisy inputs.
For an account of statistical estimation, see estimator.
The ability to accurately estimate the time/cost taken for a project to come to its successful conclusion has been a serious problem for software engineers. The use of repeatable, clearly defined and well understood software development process has in recent years shown itself to be the most effective method of gaining useful historical data that can be used for statistical estimation. In particular, the act of sampling more frequently, coupled with the loosening of constraints between parts of a project, has allowed more accurate estimation and more rapid development times.
In statistics, an estimator is a function of the known sample data that is used to estimate an unknown population parameter; an estimate is the result from the actual application of the function to a particular set of data.
The standard deviation of an estimator of θ (the square root of the variance), or an estimate of the standard deviation of an estimator of θ, is called the standard error of θ.