Damaraju Raghavarao

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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)
We show that the balanced crossover designs given by Patterson [Biometrika 39 (1952) 32–48] are (a) universally optimal (UO) for the joint estimation of direct and residual effects when the competing class is the class of connected binary designs and (b) UO for the estimation of direct (residual) effects when the competing class of designs is the class 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)
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)
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