For a given statistical model $\mathsf{P}$ it may happen that the order statistic is complete for each IID model based on $\mathsf{P}$. After reviewing known relevant results for large nonparametric models and pointing
out generalizations to small nonparametric models, we essentially prove that this happens generically even in smooth parametric models.
¶ As a consequence it may be argued that any statistic depending symmetrically on the observations can be regarded as an optimal unbiased estimator of its expectation.
¶ In particular, the sample mean $\overline{X}_n$ is generically an optimal unbiased estimator, but, as it turns out, also generically asymptotically inefficient.
@article{1032526968,
author = {Mattner, L.},
title = {Complete order statistics in parametric models},
journal = {Ann. Statist.},
volume = {24},
number = {6},
year = {1996},
pages = { 1265-1282},
language = {en},
url = {http://dml.mathdoc.fr/item/1032526968}
}
Mattner, L. Complete order statistics in parametric models. Ann. Statist., Tome 24 (1996) no. 6, pp. 1265-1282. http://gdmltest.u-ga.fr/item/1032526968/