Estimand

An estimand is a quantity that is to be estimated in a statistical analysis.^[1] 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).^[2] 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.