摘要:

In recent years, the assessment of drug effects on quality of life (QOL), which is the ability of a person to function normally in society as perceived by the patient, has become a popular issue in clinical trials. Since the response may vary widely from patient to patient and from time to time, the questionnaire (or instrument) for assessing the QOL of patients is required to be sensitive and reliable for detection of meaningful differences. QOL measurements are known to be correlated over time and among QOL indices. In this paper, we study some statistical characteristics of a given QOL instrument, such as precision and power, using a time series model that accounts for the correlation structure of QOL measurements over time. Formulae for sample size determination for clinical trials with time-correlated outcome measurements are presented.

ISSN:1054-3406    

DOI:10.1080/10543409408835068

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor

摘要:

In this paper, the original up-and-down method, modified up-and-down method, the Robbins-Monro method, and a fixed-sample Spearman-Kärber method are compared for the point estimator as well as the confidence interval of LD50. In particular, three different designs of the modified up-and-down approach based on the combination of experiments on one test space and reduced test space are investigated. The standard normal distribution and chi-square distribution are used as tolerance distributions. Simulation results indicate that the modified up-and-down method tends to be some-what better than the original up-and-down method in terms of the mean squared error under normal tolerance distribution. In case of chi-square distribution, the modified method is shown to be substantially better when the test space is wide and the initial dose is further away from the LD50.

ISSN:1054-3406    

DOI:10.1080/10543409408835069

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor

摘要:

Unknown amounts of drug from plasma samples are determined from inverse prediction of a calibration line. A statistician's criteria for accuracy and three methods for computing precision are given.

ISSN:1054-3406    

DOI:10.1080/10543409408835070

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor

摘要:

For the determination of bioequivalence, researchers have recently shifted their emphasis from average bioequivalence alone to average and individual bioequivalence. Existing methods for assessing average bioequivalence were first developed for the standard 2 × 2 crossover design, but these methods are easily generalized to the two-treatment, ρ-period crossover designs (e.g., TRR, RTT, and TTRR, RRTT, TRRT, RTTR). With respect to individual bioequivalence, Westlake (1,2) implemented the use of parametric and distribution-free tolerance intervals for assessing individual bioequivalence. Anderson and Hauck (3) described what they call the test of individual equivalence ratios (TIER) for the same purpose. Note that these methods have been applied and/or developed only for the standard 2 × 2 crossover design. The present work extends the method of using parametric tolerance intervals for assessing individual bioequivalence.

ISSN:1054-3406    

DOI:10.1080/10543409408835071

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor

摘要:

The problem of estimating parameters and testing hypotheses pertaining to categorical data is well known in statistical analysis. Much of the literature on the subject specifies and fits linear models to multinomial data using methods such as weighted least squares. This article describes maximum-likelihood estimation and likelihood ratio tests for ordered categorical response variates with either discrete or continuous underlying probability distributions. Emphasis is on fitting and making inferences about parameters of mixture distributions, especially mixtures of normal distributions. Goodness-of-fit tests are given to check the adequacy of the fitted distributional models.

ISSN:1054-3406    

DOI:10.1080/10543409408835072

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor

摘要:

A common problem encountered in bioequivalence studies is the presence of outliers. In this situation, the two one-sidedt-tests proposed by Schuirmann fail to provide reasonable power for concluding bioequivalence. In contrast, our proposed 2β trimmed-tprocedure has the following advantages: (1) it has higher efficiency for nonnormal symmetric distributions, (2) it is resistant to outliers, and (3) it is relatively easy to compute. Two bootstrap procedures introduced here provide further justification for the proposed trimmedt-test procedure. Results from Monte Carlo studies illustrate the power of the proposed procedures under various distributional assumptions for a 2 × 2 crossover trial.

ISSN:1054-3406    

DOI:10.1080/10543409408835073

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor

摘要:

A randomized, double-blind, placebo-controlled two-period crossover trial was conducted at two centers to evaluate felbamate for treatment of partial seizures in patients receiving concomitant treatment with two standard antiepileptic drugs, phenytoin and carbamazepine.

ISSN:1054-3406    

DOI:10.1080/10543409408835074

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor

摘要:

Improved methods of human immunodeficiency virus isolation have sparked an increased interest in determination of the number and proportion of infected cells in plasma samples. The limiting dilution assay is a popular method of determining the proportion of infected cells. We propose a new estimator of the proportion of infected cells based on an underlying Markov chain model for the progression of infected cells to further flasks in the series. This method should improve both design and analyses of these assays.

ISSN:1054-3406    

DOI:10.1080/10543409408835075

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor

摘要:

How long a dementia patient is cared for in the home before admission to a nursing home depends on the state of the patient and the state of the caregiver. Using 5-year follow-up data, the times until entry to nursing home and until death are modeled using a Cox survival model in which patient and caregiver variables at entry to study as well as changes in these variables over the following 12 months are the regression variables. Treatment variables quantify the effects of a caregiver training program. Statistical methods used in fitting the Cox survival model and consequent predictions of survival rates are discussed.

ISSN:1054-3406    

DOI:10.1080/10543409408835076

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor

ISSN:1054-3406    

DOI:10.1080/10543409408835067

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor