Uttam Bandyopadhyay

Abstract: SUMMARY Adaptive designs are often used in clinical trials to force balance in sequential allocation of patients between two or more competitive treatments. Sometimes, from ethical considerations, the goal may be to allocate a larger number of patients to the better treatment in the course of the trial. In the present paper we consider patients who are heterogeneous with respect to some prognostic factors and assume that the response from each patient is a continuous variable. We consider a normal linear model and provide an allocation design with due attention to the prognostic factors. The loss of efficiency incurred by using a balanced design is also indicated. Issues of inference based on adaptive allocation are also discussed. Finally a guideline is provided for the appropriate choice of the design parameters.

Abstract: In the present work, we develop a two-stage allocation rule for binary response using the log-odds ratio within the Bayesian framework allowing the current allocation to depend on the covariate value of the current subject. We study, both numerically and theoretically, several exact and limiting properties of this design. The applicability of the proposed methodology is illustrated by using some data set. We compare this rule with some of the existing rules by computing various performance measures.

Abstract: A randomized two-stage adaptive Bayesian design is proposed and studied for allocation and comparison in a phase III clinical trial with survival time as treatment response. Several exact and limiting properties of the design and the follow-up inference are studied, both numerically and theoretically, and are compared with a single-stage randomized procedure. The applicability of the proposed methodology is illustrated by using some real data.

Abstract: In the present work, we introduce a partial sequential sampling scheme to develop a sequential rank-based nonparametric test for the identity of two unknown univariate continuous distribution functions against one-sided shift in location occurring at an unknown time point. Our work is motivated by Wolfe (1977) as well as Orban and Wolfe (1980). We provide detailed discussion on asymptotic studies related to the proposed test. We compare the proposed test with a usual rank-based test. Some simulation studies are also presented.

Abstract: In the context of comparing two treatments in clinical trials, randomized play-the-winner rule is used with a goal to treat more patients by the better treatment. On its basis some decision rules are proposed taking delayed response into account. Some exact and asymptotic results of the decision rules are studied. Minimax decison rule is also obtained.

Abstract: Convergence of Probability Measures. By P. Billingsley. Chichester, Sussex, Wiley, 1968. xii, 253 p. 9 1/4“. 117s.

Abstract: (1976). Survival Distributions: Reliability Applications in the Biomedical Sciences. Technometrics: Vol. 18, No. 4, pp. 501-501.

Abstract: We propose a flexible method of extending a study based on conditional power. The possibility for extension when the p value at the planned end is small but not statistically significant is built in to the design of the study. The significance of the treatment difference at the planned end is used to determine the number of additional observations needed and the critical value necessary for use after accruing those additional observations. It may therefore be thought of as a two-stage procedure. Even though the observed treatment difference at stage 1 is used to make decisions, the Type I error rate is protected.