Editing Point estimation (section)

=== Efficiency ===
Let ''T''<sub>1</sub> and ''T''<sub>2</sub> be two unbiased estimators for the same parameter ''θ''. The estimator ''T''<sub>2</sub> would be called ''more efficient'' than estimator ''T''<sub>1</sub> if Var(''T''<sub>2</sub>) ''<'' Var(''T''<sub>1</sub>), irrespective of the value of ''θ''.<ref name=":0"/> We can also say that the most efficient estimators are the ones with the least variability of outcomes. Therefore, if the estimator has smallest variance among sample to sample, it is both most efficient and unbiased. We extend the notion of efficiency by saying that estimator T<sub>2</sub> is more efficient than estimator T<sub>1</sub> (for the same parameter of interest), if the MSE([[Mean squared error|mean square error]]) of T<sub>2</sub> is smaller than the MSE of T<sub>1</sub>.<ref name=":0"/>

Generally, we must consider the distribution of the population when determining the efficiency of estimators. For example, in a [[normal distribution]], the mean is considered more efficient than the median, but the same does not apply in asymmetrical, or [[Skewed distribution|skewed]], distributions.