A program or operator which, when applied to a system or circuit representation, can obtain an estimate of some parameter or value, e g , power, speed, or manufacturing yield (SM*)
An estimator is a rule for "guessing" the value of a population parameter based on a random sample from the population An estimator is a random variable, because its value depends on which particular sample is obtained, which is random A canonical example of an estimator is the sample mean, which is an estimator of the population mean