A truncated sequential procedure is constructed for estimating the drift
coefficient at a given state point based on discrete data of ergodic diffusion
process. A nonasymptotic upper bound is obtained for a pointwise absolute error
risk. The optimal convergence rate and a sharp constant in the bounds are found
for the asymptotic pointwise minimax risk. As a consequence, the efficiency is
obtained of the proposed sequential procedure.Comment: Published at http://dx.doi.org/10.3150/14-BEJ655 in the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
