# What is an estimator?

A point estimate is a mathematical function used from a sample to derive a value like wages or height in the population.

It is a calculation from a sample taken from the main population, trying to give you a value from tha main population.

Let’s say we get talke 1.000 people from the whole US population as a sample.

Here, we define a mathematical funcion (estimator) to derive what is the median wage of the entire population, “estimating” what the median wage of the entire population is.

An estimator has 3 main characteristics:

1. Unbiased: the expected value equals the true value of the population

2. Consistent: the greater the sample, the more accurate it is.

3 .Efficient: the most efficient estimator is the one with the smallest variance of all the unbiased and consistent estimators.

To make calculations  with a sample population below is a table showing how to calculate the mean and the standard deviation.

In rough terms, essentially comes down to using N-1 as the value for the sample population.