共查询到20条相似文献,搜索用时 15 毫秒
1.
V. K. Srivastava G. D. Mishra A. Chaturvedi 《Biometrical journal. Biometrische Zeitschrift》1981,23(1):1-8
For a linear regression model with random coefficients, this paper considers the estimation of the mean of coefficient vector which, in turn, involves the estimation of variances of random coefficients. The conventional estimation methods for it sometimes provides negative estimates. In order to circumvent this kind of difficulty, a proposal is forwarded and is examined in the light of existing ones. 相似文献
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Erkki P. Liski 《Biometrical journal. Biometrische Zeitschrift》1989,31(3):313-316
Conditions for superiority of the minimum dispersion estimator over another with respect to the covariance matrix are derived when the vector parameter of a regression model is subject to competing stochastic restrictions. The restrictions may also consist both of a deterministic part and a stochastic part. 相似文献
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J. K. Baksalary 《Biometrical journal. Biometrische Zeitschrift》1984,26(5):555-557
The minimum dispersion linear unbiased estimators of the vector of parameters in a linear regression model are compared when the parameters of the model are subject to stochastic linear restrictions with different dispersion matrices of the disturbances involved in them. 相似文献
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Gtz Trenkler 《Biometrical journal. Biometrische Zeitschrift》1993,35(1):125-128
In his recent paper Liski (1989) derived conditions for superiority of the minimum dispersion estimator over another with respect to the covariance matrix when the parameter vector of a regression model is subject to competing stochastic restrictions. The aim of this note is to provide another necessary and sufficient condition which admits an easier interpretation of superiority related to the covariance matrix criterion. 相似文献
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M. A. F. Aboukalam 《Biometrical journal. Biometrische Zeitschrift》1997,39(2):171-181
In classical linear regression model for analysis of medical data concerning hepatic extraction of insulin and c-peptide the fundamental assumption is that the subjects involved are of a similar nature. In reality, if this assumption is violated then the precision of the results is questionable. This paper suggests a robust alternative to overcome this problem. It is observed that the robustification may be a better option to determine an optimal quantity of insulin which minimizes the risk of damage associated with diabatic treatments. 相似文献
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H. Toutenburg 《Biometrical journal. Biometrische Zeitschrift》1983,25(5):501-508
If one has prior information on the unknown parameter vector β of a linear model such that ß may be assumed to lie in a concentration ellipsoid, then the resulting minimax linear estimator (MILE) is of ridge type and has smaller quadratic risk than the GLSE. This holds whenever the prior information is a true one. The relation between MILE and GLSE is investigated under incorrect specified prior regions. The MILE is said to be robust against misspecification of the prior region, if its risk stays smaller than the risk of the GLSE. 相似文献
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B. Hosmane 《Biometrical journal. Biometrische Zeitschrift》1988,30(8):925-929
A new modification of Berkson's minimum logit chi-squared estimator in simple linear logistic regression is suggested in order to achieve reduction of first order bias of the estimator as well as in the model. Furthermore, unlike estimators currently available, our procedure is quite simple to apply in practice and is valid even in the presence of zero frequencies in the table. 相似文献
9.
Jyrki Mttonen Hannu Oja Ulf Krause Paula Rantakallio 《Biometrical journal. Biometrische Zeitschrift》1995,37(6):657-672
A one-year birth cohort from Northern Finland has been followed up since 1966. As a part of this study, we are in this paper concerned with analysing the progression of myopia (nearsightness) up to the age of 20 years. The random coefficient regression model was chosen for the analysis because of the large individual variation in the development of myopia. Maximum likelihood estimates for the parameters in the model were obtained via the expectation maximization (EM) algorithm. It is shown how the estimated model can be used to predict future observations for an individual using the previously recorded refractive error measurements as well as other relevant data on the patient in question. 相似文献
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Emmanuel Lesaffre David Todem Geert Verbeke Mike Kenward 《Biometrical journal. Biometrische Zeitschrift》2000,42(7):807-822
A flexible approach is proposed for modelling the covariance matrix of a linear mixed model for longitudinal data. The method combines parametric modelling of the random effects part with flexible modelling of the serial correlation component. The approach is exemplified on weight gain data and on the evolution of height of children in their first year of life of the Jimma Infant Survival Study, an Ethiopian cohort study. The analyses show the usefulness of the approach. 相似文献
12.
C. Stepniak 《Biometrical journal. Biometrische Zeitschrift》1984,26(7):815-816
Let Y be observable random vector such that EY=Xβ and D(Y)=ρ2V. Linear estimation of a parameter p′β under the squared loss is considered. RAO, 1976 and 1979, obtained a necessary and sufficient condition for admissibility of an estimator t′Y in the case X=I. This result will be extended for arbitrary X. AMS 1970 subject classifications. Primary 62J05; secondary 62C15. 相似文献
13.
Ionut Bebu Françoise Seillier‐Moiseiwitsch Thomas Mathew 《Biometrical journal. Biometrische Zeitschrift》2009,51(6):1047-1058
The problem of constructing a confidence interval for the ratio of two regression coefficients is addressed in the context of multiple regression. The concept of a Generalized Confidence Interval is used, and the resulting confidence interval is shown to perform well in terms of coverage probability. The proposed methodology always results in an interval, unlike the confidence region generated from Fieller's theorem. The procedure can easily be implemented for parallel‐line assays, slope‐ratio assays, and quantal assays under a probit model. Furthermore, this approach can also be extended to compute confidence intervals based on data from multiple bioassays. The results are illustrated using several examples. 相似文献
14.
Frank Gilberg Wolfgang Urfer Lutz Edler 《Biometrical journal. Biometrische Zeitschrift》1999,41(5):543-557
We present a new modification of nonlinear regression models for repeated measures data with heteroscedastic error structures by combining the transform-both-sides and weighting model from Caroll and Ruppert (1988) with the nonlinear random effects model from Lindstrom and Bates (1990). The proposed parameter estimators are a combination of pseudo maximum likelihood estimators for the transform-both-sides and weighting model and maximum likelihood (ML) or restricted maximum likelihood (REML) estimators for linear mixed effects models. The new method is investigated by analyzing simulated enzyme kinetic data published by Jones (1993). 相似文献
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The method of mixed regression is considered for the estimation of coefficients in a linear regression model when incomplete prior information is available, and two families of improved estimators stemming from Stein-rule are proposed. Their properties are studied when disturbances are normal but small. 相似文献
17.
A linear regression approach is presented for the statistical analysis of dose-response curves obtained by measuring the colony-forming ability of human fibroblast strains. The crucial determination of the dose range in which the linear model can be assumed is achieved by a combination of statistical criteria and biological claims. As a basic quantitative parameter we investigate the slope of the regression line and, by taking reciprocals, we retransform it into the biologically established parameter D0. Several methods for the combination of estimates are presented. 相似文献
18.
The model used in this paper is Y = Xβ, where with unknown x0. Estimators of x0 are derived by putting βmx0 =βm+1 regarding βm+1 as a new unknown parameter. Formally we use the model Y = X1β+ + e where β′+ = (β0, …βm+1 and Then βm+1/ βm is a point estimator of x0. Assuming normality for e and taking the random variable z=βmx0?βm+1 we get a t-distributed variable and finally a confidence estimator of x0. The formulas are applied in dose response relations in antibiotic assays refering to a standard. Now we can take into account not only the dependence on the dose/concentration but also on the position on the test agar plate where the test solution is filled in. As a consequence the confidence interval of the unknown dose/concentration x0 becomes shorter and by it the statements more precise. 相似文献
19.
Semiparametric Regression in Size-Biased Sampling 总被引:1,自引:0,他引:1
Ying Qing Chen 《Biometrics》2010,66(1):149-158
Summary . Size-biased sampling arises when a positive-valued outcome variable is sampled with selection probability proportional to its size. In this article, we propose a semiparametric linear regression model to analyze size-biased outcomes. In our proposed model, the regression parameters of covariates are of major interest, while the distribution of random errors is unspecified. Under the proposed model, we discover that regression parameters are invariant regardless of size-biased sampling. Following this invariance property, we develop a simple estimation procedure for inferences. Our proposed methods are evaluated in simulation studies and applied to two real data analyses. 相似文献
20.
M. Bartko 《Biometrical journal. Biometrische Zeitschrift》1984,26(3):271-277
The covariance matrix of the least-squares-estimator for the coefficients of the mixed model of linear regression is deduced. This serves as a base to work out procedures experimental design for point and confidence estimations of the regression coefficients and the regression function. So it was shown, that the C-, A-, D- and G-optimal designs in the mixed model are the same as in model I. Further an assertion for sample size determination is proved especially for point estimation of the regression function. 相似文献