Estimand

An estimand is a quantity that is to be estimated in a statistical analysis. The term is used to distinguish the target of inference from the method used to obtain an approximation of this target (i.e., the estimator) and the specific value obtained from a given method and dataset (i.e., the estimate). For instance, a normally distributed random variable ${\displaystyle X}$ has two defining parameters, its mean ${\displaystyle \mu }$ and variance ${\displaystyle \sigma ^{2}}$. A variance estimator:

${\displaystyle s^{2}=\sum _{i=1}^{n}\left.\left(x_{i}-{\bar {x}}\right)^{2}\right/(n-1)}$,

yields an estimate of 7 for a data set ${\displaystyle x=\left\{2,3,7\right\}}$; then ${\displaystyle s^{2}}$ is called an estimator of ${\displaystyle \sigma ^{2}}$, and ${\displaystyle \sigma ^{2}}$ is called the estimand.