摘要:

The multivariate linear modelis used to analyze data in 2 X 2 crossover designs with either univariate or multivariate response. Diagnostics are performed on estimating the effect of interest formulated asCβUand on testing the general linear hypothesisCβU=k.The multivariate Cook's distance is extended to be the influence measure by incorporating the contrast matrixCand the transformation matrixU, and, the difference between the F approximation of a multivariate test statistic, is proposed as a measure to detect influential observations for testing the hypothesisCβU=k.Both measures prove to be very useful because the diagnostics are now associated with estimating and testing effects of interest in the context of the experimental design.

ISSN:1054-3406    

DOI:10.1080/10543409408835088

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor

摘要:

Four multidose animal carcinogenicity assay trend test procedures based on the chi-square, Hoel-Walburg, log-rank, and Peto procedures are compared under conditions of competing risks. A total of 42 different risk populations are simulated in which a simulated animal can contract one or more of five different tumor types. The risk populations contain such different risks as incidence of tumor increasing with dose, time of death increasing or decreasing with dose, tumor decreasing time of death without necessarily causing death (nonrepresentativeness), and combinations of the above. Each population is analyzed using each of the four procedures for linear dose-response effect for each tumor separately and for all animals with tumors.

ISSN:1054-3406    

DOI:10.1080/10543409408835089

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor

摘要:

The purpose of this paper is to discuss a long-term, multiperiod crossover study to compare two treatments for migraine headache. Principal attention is given to the analysis of an example in which patients randomly received a treatment sequence with test drug for three migraine headaches and placebo for one. An issue that requires attention for this example is the influence of a carryover effect for test drug that was greater when placebo was the subsequent treatment than when test drug was the subsequent treatment. A way to address this issue without excessive loss of power is to consider tests of “total treatment effects,” which are weighted averages across headaches of differences between average response to test drug and average response to placebo. Since these weighted averages are linear combinations of treatment effects and carryover effects, their use requires an argument that carryover effects are at least partly a further form of treatment effects. For the example in this paper, this argument is realistic because the test drug could have provided much better relief to migraine headache than other treatment patients might have previously used.

ISSN:1054-3406    

DOI:10.1080/10543409408835090

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor

摘要:

This paper discusses alternative statistical models for the analysis of six crossover studies to determine whether better relief of tension headache occurs from treatment with an analgesic plus caffeine (C) than with the analgesic alone (A) or with placebo (P). Each patient in these crossover studies randomly received a pair of distinct medications in such a way as to treat the first two of four headaches with the initial medication in the pair and to treat the third and fourth headaches with the last medication in the pair. In order to have greater power for the C versus A comparison, three times as many patients were randomly assigned to the A:C and C:A sequence groups as to the A:P, C:P, P:A, and P:C sequence groups.

ISSN:1054-3406    

DOI:10.1080/10543409408835091

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor

摘要:

Healy (1) and Dempsteret al. (8) proposed statistical methods to evaluate the treatment effects in animal reproductive toxicology research. Both methods assume homogeneous variance for the dams and the pups, respectively, in all the treatment groups. In this paper, via mixed effect modeling, we propose a method to estimate the treatment effects allowing heterogeneous variances for the dams and the pups, respectively, in different treatment groups. Covariates will also be included in the model. A procedure to test the fixed effects is also discussed. An example from an animal reproductive toxicological study is used to illustrate the procedures.

ISSN:1054-3406    

DOI:10.1080/10543409408835092

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor

摘要:

In multiple-dose bioequivalence studies, it is possible at steady state to take repeated measurements of pharmacokinetic variables, such as area under the curve (AUC) and the maximum concentration (CMAX) of the blood concentration-time profile, within each period of a crossover design. We develop a bivariate random effects model for such a situation in a 2 × 2 crossover design using the natural log scale for AUC and CMAX that assumes no differential carryover effects and includes components for inter- and intrasubject variability with respect to both formulations. We derive the uniformly minimum variance unbiased estimators, which also happen to be restricted maximum likelihood estimators, and we provide a sample size formula.

ISSN:1054-3406    

DOI:10.1080/10543409408835093

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor

摘要:

Two different methods of analyses were given for a complex experiment dealing with two sets of direct and crossover effects.

ISSN:1054-3406    

DOI:10.1080/10543409408835094

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor

ISSN:1054-3406    

DOI:10.1080/10543409408835087

出版商:Marcel Dekker, Inc.    

年代:1994

数据来源: Taylor