Sometimes,particularly when we are interested in the role of the number of observations n.we use the notation,for an estimator. It is then also appropriate to view as a sequence of estimators. One for each value of n. The mean and variance of are denoted Ea[⑥n and vare[⑥nl,respectively. We sometimes drop this subscript 0 when the context is clear. Sometimes, particularly when we are interested in the role of the number of observations 𝑛, we use the notation Θ ෡ 𝑛 for an estimator.  It is then also appropriate to view Θ ෡ 𝑛 as a sequence of estimators.  One for each value of 𝑛.  The mean and variance of Θ ෡ 𝑛 are denoted 𝐸𝜃 Θ ෡ 𝑛 and 𝑣𝑎𝑟𝜃 Θ ෡ 𝑛 , respectively.  We sometimes drop this subscript 𝜃 when the context is clear