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531.
Francesca Parpinel 《Statistical Methods and Applications》1995,4(3):357-376
Summary Maximum likelihood estimation is a well-known statistical tool. When applied to the study of dynamical continuous-time phenomena,
it requires some specific assumptions. In this paper we discuss some properties of the maximum likelihood estimator for a
stochastic Verhulst model and we show some simulation results on the behaviour of the corresponding discrete estimator. 相似文献
532.
讨论了商业、市场中大量存在的饱和增长过程的自适应预测问题,详细分析了自适应增长趋势预测尤其是Kalman滤波方法涉及的模型、模型变换、递推初值确定及趋势外椎等技术问题。 相似文献
533.
In this article, small sample properties of the maximum-likelihood estimator (m.l.e.) for the offspring distribution (pk) and its mean m are considered in the context of the simple branching process. A representation theorem is given for the m.l.e. of (Pk) from which the m.l.e. of m is obtained. The case where p0 + p1 + p2 = 1 is studied in detail: numerical results are given for the exact bias of these estimators as a function of the age of the process; a curve fitting analysis expresses the bias of m? as a function of the mean and the variance of the offspring distribution and finally an “approximate m.l.e.” for (pk) is given. 相似文献
534.
Alain Boulanger 《Revue canadienne de statistique》1983,11(4):271-284
This paper is concerned with the estimation of a shift parameter δo, based on some nonnegative functional Hg1 of the pair (DδN(x), f?δN(x)), where DδN(x) = KN/b {F2,n(x)—F1,m (x + δ)}, +δN(x) = {mF1,m (x + δ) + nF2,n(x)}/N, where F1,m and F2,n are the empirical distribution functions of two independent random samples (N = m + n), and where K2N = mn/N. First an estimator δN, is defined as a value of δ minimizing a functional H of the type of H1. A second estimator δ1N is also defined which is a linearized version of the first. Finite and asymptotic properties of these estimators are considered. It is also shown that most well-known test statistics of the Kolmogorov-Smirnov type are particular cases of such functionals H1. The asymptotic distribution and the asymptotic efficiency of some estimators are given. 相似文献
535.
We consider the problem of binary-image restoration. The image being restored is not random, and we make no assumption about the nature of its contents. The estimate of the colour at each site is a fixed (the same for all sites) function of the data available in a neighbourhood of that site. Under this restriction, the estimate minimizing the overall mean squared error of prediction is the conditional expectation of the true colour given the observations in the neighbourhood of a site. The computation of this conditional expectation leads to the formal definition of the local characteristics of an image, namely, the frequency with which each pattern appears in the true unobserved image. When the “true” distribution of the patterns is unknown, it can be estimated from the records. The conditional expectation described above can then be evaluated using the estimated distribution of the patterns, and this procedure leads to a very natural estimate of the colour at each site. We propose two unbiased and consistent estimates for the distribution of patterns when the noise is a Gaussian white noise. Since the size of realistic images is very large, the estimated pattern distribution is usually close to the true one. This suggests that the estimated conditional expectation can be expected to be nearly optimal. An interesting feature of the proposed restoration methods is that they do not require prior knowledge of the local or global properties of the true underlying image. Several examples based on synthetic images show that the new methods perform fairly well for a variety of images with different degrees of colour continuity or textures. 相似文献
536.
Dankmar Bhning 《Statistical Methodology》2008,5(5):410-423
This note considers the variance estimation for population size estimators based on capture–recapture experiments. Whereas a diversity of estimators of the population size has been suggested, the question of estimating the associated variances is less frequently addressed. This note points out that the technique of conditioning can be applied here successfully which also allows us to identify sources of variation: the variance due to estimation of the model parameters and the binomial variance due to sampling n units from a population of size N. It is applied to estimators typically used in capture–recapture experiments in continuous time including the estimators of Zelterman and Chao and improves upon previously used variance estimators. In addition, knowledge of the variances associated with the estimators by Zelterman and Chao allows the suggestion of a new estimator as the weighted sum of the two. The decomposition of the variance into the two sources allows also a new understanding of how resampling techniques like the Bootstrap could be used appropriately. Finally, the sample size question for capture–recapture experiments is addressed. Since the variance of population size estimators increases with the sample size, it is suggested to use relative measures such as the observed-to-hidden ratio or the completeness of identification proportion for approaching the question of sample size choice. 相似文献
537.
本文介绍了一种实用自适应PID控制器,它是以MCS-51系列单片微机为核心,采用PID控制规律结合参数辨识的控制算法,实现了PID参数完全在线自动整定。该控制器适用于被控制对象未知或慢时变的场合,既可替代常规PID控制器,也可作为分布式系统的低级智能控制器。 相似文献
538.
It is assumed that a large random sample of fixed size n is drawn from a logarithmic series distribution with parameter $tH and that it is desired to estimate e by means of two-sided confidence interval. Using asymptotic results, charts of confidence intervals are prepared for n = 50, 100, 200, 500 and 1,000, and confidence coefficients 0.90 and 0.95. 相似文献
539.
540.
Luc Devroye 《Revue canadienne de statistique》1979,7(2):159-167
Let f be an unknown possibly multimodal density on Rd and let X1, X2, … be a sequence of independent random vectors with density f. Several recursive estimates of the mode of f are proposed, and sufficient conditions ensuring their weak and strong consistency are established. 相似文献