Estimator

probability-theory

Variance

Variance of an Estimator

The variance of an estimator $\hat{\theta }$ measures how much $\hat{\theta }$ fluctuates around its expected value:

$$\mathrm{Var}(\hat{\theta })=\mathbb{E}[(\hat{\theta }-\mathbb{E}[\hat{\theta }]{)}^2]$$

A smaller variance implies a more precise estimator.