An estimator is any value calculated from the sample data For example, the sample mean is an estimator of the population mean.

A random variable that can be calculated from sample data which is used to give information about an unknown quantity in the population. For example, the sample mean is an estimator of the population mean. Each observed sample gives a value of the estimator.

an expert at calculation (or at operating calculating machines)

a formula that calculates the average change in prices of sample items using current and previous period prices

a general rule for estimating from a sample

an observable random variable (i

a random variable , because its value depends on which particular sample is obtained, which is random

a rule that tells how to calculate an estimate based on the measurements contained in a sample

a specific function of the random samples, of a random variable, that statistically represents a true unknown mean

a statistic used as an approximation to a parameter

statistic that is used in place of an unknown parameter.

Uses statistics to estimate the selectivity, cardinality, and cost of execution plans. The main goal of the estimator is to estimate the overall cost of an execution plan.

In statistics, an estimator is a function of the observable 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. Many different estimators are possible for any given parameter. Some criterion is used to choose between the estimators, although it is often the case that a criterion cannot be used to clearly pick one estimator over another.