Abstract: The article proposes a computationally efficient procedure for bias adjustment in the iterated bootstrap. The new technique replaces the need for successive levels of bootstrap resampling by proposing an approximation for the double bootstrap “calibrating coefficient” using only one draw from the second level probability distribution. Extensive Monte Carlo evidence suggest that the pr...

In this paper we describe a methodology for determining corrections to parameters and initial conditions in order to improve model forecasts in the presence of data. This methodology is grounded in the variational problem of minimizing the norm of the errors between forecast and data. The general method is presented, and then the method is applied to the specific example of a scalar model, the ...

This paper discusses methods for reducing the bias of consistent estimators that are biased in nite samples. These methods are available whenever the bias function, which relates the bias of the parameter estimates to the values of the parameters, can be estimated by computer simulation or by some other method. If so, bias can be reduced by one full order in the sample size and, in some cases t...

We propose a novel bias correction method for magnetic resonance (MR) imaging that uses complementary body coil and surface coil images. The former are spatially homogeneous but have low signal intensity; the latter provide excellent signal response but have large bias fields. We present a variational framework where we optimize an energy functional to estimate the bias field and the underlying...

Seasonal variation in habitat selection by the mountain goat Oreamnos americanus is not well understood due to the difficulties of monitoring animal movement in all months of the year. The use of global positioning system (GPS) wildlife telemetry collars offers an opportunity to overcome this obstacle, however satellite acquisition problems associated with GPS wildlife telemetry collars create ...

BACKGROUND Scientists often use a paired comparison of the areas under the receiver operating characteristic curves to decide which continuous cancer screening test has the best diagnostic accuracy. In the paired design, all participants are screened with both tests. Participants with suspicious results or signs and symptoms of disease receive the reference standard test. The remaining particip...

Results of numerous evaluation studies indicated that satellite-rainfall products are contaminated with significant systematic and random errors. Therefore, such products may require refinement and correction before being used for hydrologic applications. In the present study, we explore a rainfall-runoff modeling application using the Climate Prediction Center-MORPHing (CMORPH) satellite rainf...

Author Contact: David E. Giles, Dept. of Economics, University of Victoria, P.O. Box 1700, STN CSC, Victoria, B.C., Canada V8W 2Y2; e-mail: [email protected]; Phone: (250) 721-8540; FAX: (250) 721-6214 Abstract We consider the quality of the maximum likelihood estimators for the parameters of the two-parameter gamma distribution in small samples. We show that the methodology suggested by Cox and S...