Estimator
In statistics, an estimator is a rule for calculating an estimate of a given amount based on observed data: thus the rule (the estimator), the amount that is being measured (the estimand) and its result (the estimate) are different.
An estimator of a parameter is often written as. If the expected value of the estimator is equal to the parameter, then the estimator is called unbiased. Otherwise, it is called biased.
Related pages
Efficiency (statistics)
References
Other websites
Fundamentals on Estimation Theory
Statistics