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排序方式: 共有628条查询结果,搜索用时 15 毫秒
1.
We consider the problem of estimating a probability density function based on data that are corrupted by noise from a uniform distribution. The (nonparametric) maximum likelihood estimator for the corresponding distribution function is well defined. For the density function this is not the case. We study two nonparametric estimators for this density. The first is a type of kernel density estimate based on the empirical distribution function of the observable data. The second is a kernel density estimate based on the MLE of the distribution function of the unobservable (uncorrupted) data. 相似文献
2.
本文讨论了一类新的加工时间可控的单机排序问题,其目标函数为正则函数与最大不满意程度函数之和,不满意函数刻划了对工件实际加工时间偏离其额定加工时间不满意的程度,本文对这类问题提出了几个多项式算法。 相似文献
3.
Estimation in the interval censoring model is considered. A class of smooth functionals is introduced, of which the mean is an example. The asymptotic information lower bound for such functionals can be represented as an inner product of two functions. In case 1, i.e. one observation time per unobservable event time, both functions can be given explicitly. We mainly consider case 2, with two observation times for each unobservable event time, in the situation that the observation times can not become arbitrarily close to each other. For case 2, one of the functions in the inner product can only be given implicitly as solution to a Fredholm integral equation. We study properties of this solution and, in a sequel to this paper, prove that the nonparametric maximum likelihood estimator of the functional asymptotically reaches the information lower bound. 相似文献
4.
An extensive collection of continuous-time models of the short-term interest rate is evaluated over data sets that have appeared previously in the literature. The analysis, which uses the simulated maximum likelihood procedure proposed by Durham and Gallant (2002), provides new insights regarding several previously unresolved questions. For single factor models, I find that the volatility, not the drift, is the critical component in model specification. Allowing for additional flexibility beyond a constant term in the drift provides negligible benefit. While constant drift would appear to imply that the short rate is nonstationary, in fact, stationarity is volatility-induced. The simple constant elasticity of volatility model fits weekly observations of the three-month Treasury bill rate remarkably well but is easily rejected when compared with more flexible volatility specifications over daily data. The methodology of Durham and Gallant can also be used to estimate stochastic volatility models. While adding the latent volatility component provides a large improvement in the likelihood for the physical process, it does little to improve bond-pricing performance. 相似文献
5.
Robustness issues in multilevel regression analysis 总被引:8,自引:0,他引:8
A multilevel problem concerns a population with a hierarchical structure. A sample from such a population can be described as a multistage sample. First, a sample of higher level units is drawn (e.g. schools or organizations), and next a sample of the sub‐units from the available units (e.g. pupils in schools or employees in organizations). In such samples, the individual observations are in general not completely independent. Multilevel analysis software accounts for this dependence and in recent years these programs have been widely accepted. Two problems that occur in the practice of multilevel modeling will be discussed. The first problem is the choice of the sample sizes at the different levels. What are sufficient sample sizes for accurate estimation? The second problem is the normality assumption of the level‐2 error distribution. When one wants to conduct tests of significance, the errors need to be normally distributed. What happens when this is not the case? In this paper, simulation studies are used to answer both questions. With respect to the first question, the results show that a small sample size at level two (meaning a sample of 50 or less) leads to biased estimates of the second‐level standard errors. The answer to the second question is that only the standard errors for the random effects at the second level are highly inaccurate if the distributional assumptions concerning the level‐2 errors are not fulfilled. Robust standard errors turn out to be more reliable than the asymptotic standard errors based on maximum likelihood. 相似文献
6.
In this paper, progressive stress accelerated life tests are considered when the lifetime of a product under use condition
follows a finite mixture of distributions. The experiment is performed when each of the components in the mixture follows
a general class of distributions which includes, among others, the Weibull, compound Weibull, power function, Gompertz and
compound Gompertz distributions. It is assumed that the scale parameter of each component satisfies the inverse power low,
the progressive stress is directly proportional to time and the cumulative exposure model for the effect of changing stress
holds. Based on type-I censoring, the maximum likelihood estimates (MLEs) of the parameters under consideration are obtained.
A special attention is paid to a mixture of two Rayleigh components. Simulation results are carried out to study the precision
of the MLEs and to obtain confidence intervals for the parameters involved. 相似文献
7.
Although conceptually pleasing, normal-gamma frontier models lead to difficult estimation problems. It is shown here that unless the sample size reaches several thousands of observations the shape parameter of the gamma density is hard to estimate, and that this carries over to estimates of the stochastic frontier, the individual inefficiencies, and the allocation of the overall variance to the stochastic frontier and to the inefficiencies. 相似文献
8.
Abstract. In this paper we study the first–order efficiency and asymptotic normality of the maximum likelihood estimator obtained from dependent observations. Our conditions are weaker than usual, in that we do not require convergences in probability to be uniform or third–order derivatives to exist.
The paper builds on Witting and Nolle's result concerning the asymptotic normality of the maximum likelihood estimator obtained from independent and identically distributed observations, and on a martingale theorem by McLeish. 相似文献
The paper builds on Witting and Nolle's result concerning the asymptotic normality of the maximum likelihood estimator obtained from independent and identically distributed observations, and on a martingale theorem by McLeish. 相似文献
9.
In this paper, we propose an estimator for the population mean when some observations on the study and auxiliary variables
are missing from the sample. The proposed estimator is valid for any unequal probability sampling design, and is based upon
the pseudo empirical likelihood method. The proposed estimator is compared with other estimators in a simulation study. 相似文献
10.
上海股市收益与波动的周内效应研究 总被引:2,自引:0,他引:2
股市周内效应一直是金融投资者关注的焦点问题,许多学者已做了大量研究,但多数文献将收益与波动的周内效应分开来进行研究和检验,忽视了波动与收益的共生性,其结果缺乏严密性和说服力。针对这种情况,提出平行数据GARCH模型并给出了参数的极大似然估计方法,进而对上海股市收益和波动的周内效应进行检验,既反映收益与风险存在共生关系,又避免了分别判断收益和波动的周内效应所致的缺点。 相似文献