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Resulting Estimates (resulting + estimate)
Selected AbstractsA Multiple Imputation Approach to Cox Regression with Interval-Censored DataBIOMETRICS, Issue 1 2000Wei Pan Summary. We propose a general semiparametric method based on multiple imputation for Cox regression with interval-censored data. The method consists of iterating the following two steps. First, from finite-interval-censored (but not right-censored) data, exact failure times are imputed using Tanner and Wei's poor man's or asymptotic normal data augmentation scheme based on the current estimates of the regression coefficient and the baseline survival curve. Second, a standard statistical procedure for right-censored data, such as the Cox partial likelihood method, is applied to imputed data to update the estimates. Through simulation, we demonstrate that the resulting estimate of the regression coefficient and its associated standard error provide a promising alternative to the nonparametric maximum likelihood estimate. Our proposal is easily implemented by taking advantage of existing computer programs for right,censored data. [source] Properties of case/pseudocontrol analysis for genetic association studies: Effects of recombination, ascertainment, and multiple affected offspringGENETIC EPIDEMIOLOGY, Issue 3 2004Heather J. Cordell Abstract The case/pseudocontrol approach is a general framework for family-based association analysis, incorporating several previously proposed methods such as the transmission/disequilibrium test and log-linear modelling of parent-of-origin effects. In this report, I examine the properties of methods based on a case/pseudocontrol approach when applied to a linked marker rather than (or in addition to) the true disease locus or loci, and when applied to sibships that have been ascertained on, or that may simply contain, multiple affected sibs. Through simulations and analytical calculations, I show that the expected values of the observed relative risk parameters (estimating quantities such as effects due to a child's own genotype, maternal genotype, and parent-of-origin) depend crucially on the ascertainment scheme used, as well as on whether there is non-negligible recombination between the true disease locus and the locus under study. In the presence of either recombination or ascertainment on multiple affected offspring, methods based on conditioning on parental genotypes are shown to give unbiased genotype relative risk estimates at the true disease locus (or loci) but biased estimates of population genotype relative risks at a linked marker, suggesting that the resulting estimates may be misleading when used to predict the power of future studies. Methods that allow for exchangeability of parental genotypes are shown (in the presence of either recombination or ascertainment on multiple affected offspring) to produce false-positive evidence of maternal genotype effects when there are true parent-of-origin or mother-child interaction effects, even when analyzing the true locus. These results suggest that care should be taken in both the interpretation and application of parameter estimates obtained from family-based genetic association studies. © 2004 Wiley-Liss, Inc. [source] Determination of regional net radiation and soil heat flux over a heterogeneous landscape of the Tibetan PlateauHYDROLOGICAL PROCESSES, Issue 15 2002Yaoming Ma Abstract This paper explores the potential for documenting regional fields of surface energy fluxes over the Tibetan plateau using published algorithms and previously calibrated empirical formulae with data from NOAA-14 AVHRR and atmospheric data collected during the GAME-Tibet field experiment. Comparison with observations at three field sites suggests errors in the resulting estimates are less than 10% in the clear sky conditions necessary for application of this approach. Because of the need for clear skies, it was only possible to calculate the desired regional fields for one satellite scene during the 5 month study period. Maps of surface energy fluxes, and frequency analyses of these maps, are presented for this scene. The need for an alternative, more consistently applicable, satellite-based method to map surface energy fields is highlighted. Copyright © 2002 John Wiley & Sons, Ltd. [source] Origins, uses of, and relations between goal programming and data envelopment analysisJOURNAL OF MULTI CRITERIA DECISION ANALYSIS, Issue 1 2005W.W. Cooper Abstract Origins and uses of ,goal programming' and ,data envelopment analysis' (DEA) are identified and discussed. The purpose of this paper is not only to review some of the history of these developments, but also to show some of their uses (e.g. in statistical regression formulations) in order to suggest paths for possible further developments. Turning to how the two types of models relate to each other, the ,additive model' of DEA is shown to have the same structure as a goal programming model in which only ,one-sided deviations' are permitted. A way for formally relating the two to each other is then provided. However, the objectives are differently oriented because goal programming is directed to future performances as part of the planning function whereas DEA is directed to evaluating past performances as part of the control function of management. Other possible ways of comparing and combining the two approaches are also noted including statistical regressions that utilize goal programming to ensure that the resulting estimates satisfy the multi-criteria conditions that are often encountered in managerial applications. Both goal programming and DEA originated in actual applications that were successfully addressed. The research was then generalized and published. This leads to what is referred to as an ,applications-driven theory' strategy for research that is also described in this paper. Copyright © 2006 John Wiley & Sons, Ltd. [source] Modelling long-term pan-European population change from 1870 to 2000 by using geographical information systemsJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES A (STATISTICS IN SOCIETY), Issue 1 2010Ian N. Gregory Summary., The paper presents work that creates a geographical information system database of European census data from 1870 to 2000. The database is integrated over space and time. Spatially it consists of regional level data for most of Europe; temporally it covers every decade from 1870 to 2000. Crucially the data have been interpolated onto the administrative units that were available in 2000, thus allowing contemporary population patterns to be understood in the light of the changes that have occurred since the late 19th century. The effect of interpolation error on the resulting estimates is explored. This database will provide a framework for much future analysis on long-term Europewide demographic processes over space and time. [source] Supply, Factor Shares and Inflation Persistence: Re-examining Euro-area New-Keynesian Phillips Curves,OXFORD BULLETIN OF ECONOMICS & STATISTICS, Issue 2004Peter McAdam Abstract Using euro-area data, we re-examine the empirical success of New-Keynesian Phillips curves (NKPCs). We re-estimate with a suitably specified optimizing supply side (which attempts to treat non-stationarity in factor income shares and mark-ups) that allows us to derive estimates of technology parameters, marginal costs and ,price gaps'. Our resulting estimates of the euro-area NKPCs are robust, provide reasonable estimates for fixed-price durations and discount rates and embody plausible dynamic properties. Our method for identifying the underlying determinants of NKPCs has general applicability to a wide set of countries as well as of use for sectoral studies. [source] SIMULATED MAXIMUM LIKELIHOOD APPLIED TO NON-GAUSSIAN AND NONLINEAR MIXED EFFECTS AND STATE,SPACE MODELSAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 4 2004Russell B. Millar Summary The paper presents an overview of maximum likelihood estimation using simulated likelihood, including the use of antithetic variables and evaluation of the simulation error of the resulting estimates. It gives a general purpose implementation of simulated maximum likelihood and uses it to re-visit four models that have previously appeared in the published literature: a state,space model for count data; a nested random effects model for binomial data; a nonlinear growth model with crossed random effects; and a crossed random effects model for binary salamander-mating data. In the case of the last three examples, this appears to be the first time that maximum likelihood fits of these models have been presented. [source] Estimating Disease Prevalence Using Relatives of Case and Control ProbandsBIOMETRICS, Issue 1 2010Kristin N. Javaras Summary We introduce a method of estimating disease prevalence from case,control family study data. Case,control family studies are performed to investigate the familial aggregation of disease; families are sampled via either a case or a control proband, and the resulting data contain information on disease status and covariates for the probands and their relatives. Here, we introduce estimators for overall prevalence and for covariate-stratum-specific (e.g., sex-specific) prevalence. These estimators combine the proportion of affected relatives of control probands with the proportion of affected relatives of case probands and are designed to yield approximately unbiased estimates of their population counterparts under certain commonly made assumptions. We also introduce corresponding confidence intervals designed to have good coverage properties even for small prevalences. Next, we describe simulation experiments where our estimators and intervals were applied to case,control family data sampled from fictional populations with various levels of familial aggregation. At all aggregation levels, the resulting estimates varied closely and symmetrically around their population counterparts, and the resulting intervals had good coverage properties, even for small sample sizes. Finally, we discuss the assumptions required for our estimators to be approximately unbiased, highlighting situations where an alternative estimator based only on relatives of control probands may perform better. [source] | |||||||||||||