Damaraju Raghavarao

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We would like to estimate the parameters of a dose-response function with the greatest precision as possible. For a two-parameter model, this is equivalent to minimizing the area of the confidence ellipsoid, i.e., a D-optimal design. Previous work on this particular model has included minimal designs. These designs are unable to determine lack of fit. We(More)
In this paper the author applies Boolean sum operation on sets of certain known designs to get new series of designs. In particular certain unsYmmetrical balanced incomplete block designs can be constructed from sYmmetrical balanced incomplete block designs and triangular designs can be constructed from irreducible balanced incomplete block designs and(More)
To reduce the cost of stability testing in drug research and development, both bracketing and matrixing designs are recommended in the U.S. Food and Drug Administration's (FDA) guidelines for drug products with a single active ingredient (component). When the drug product contains multiple active components, the naïve approach is to take the minimum of(More)
In this article we focus on the optimal factorial and fractional-factorial designs when observations within blocks are correlated. The topic was motivated by a problem when the pharmaceutical experimenter needed to develop a controlled release, once-daily tablet formulation. Typically, in order to compare different formulations, trials are conducted in(More)
Interest in administering compounds in combination lies both in enhancing efficacious effects and in limiting adverse effects. Although much statistical work has focused on developing mathematical functions to model the joint dose-response curves, relatively little work exists in regard to designing experiments for assessing joint action. A variety of(More)
In this note we discuss the relationship between the underlying kinetic model and the statistical (or analytic) model used to study degradation. For small degradation rates, the zeroth, first, and second order statistical models give approximately the same fits and predictions on either the original assay scale or the percent of label claim scale. However,(More)
The constrained four parameter logistic model has found wide application in describing dose response relationships across many assay systems. This discussion examines the basic model and its practical application to potency testing in the context of the 96 well plate. A two step procedure is recommended for the analysis: (i) the constrained logistic model(More)
The use of subjective measures in the evaluation of treatment efficacy in clinical trials may introduce bias into the response variables of interest when investigators attempt to guess the treatment that patients are receiving. The bias may be introduced even in the setting of double-blind clinical trials due to the presence of characteristic side effects.(More)
In the U.S. Food and Drug Administration (FDA) guidelines for stability testing of new drug products, both bracketing and matrixing designs were suggested as the statistical designs. More recently, they have increasing attention from pharmaceutical companies, because both designs reduce the cost of stability studies. The purpose of this paper is to(More)