Combining an Internal Pilot with an Interim Analysis for Single Degree of Freedom Tests |
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Authors: | Kairalla John A Muller Keith E Coffey Christopher S |
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Institution: | Division of Biostatistics, Department of Epidemiology and Health Policy Research, College of Medicine, University of Florida. PO Box 100177, Gainesville, FL 32610, USA. |
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Abstract: | An internal pilot with interim analysis (IPIA) design combines interim power analysis (an internal pilot) with interim data analysis (two stage group sequential). We provide IPIA methods for single df hypotheses within the Gaussian general linear model, including one and two group t tests. The design allows early stopping for efficacy and futility while also re-estimating sample size based on an interim variance estimate. Study planning in small samples requires the exact and computable forms reported here. The formulation gives fast and accurate calculations of power, type I error rate, and expected sample size. |
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