Combining an Internal Pilot with an Interim Analysis for Single Degree of Freedom Tests |
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| Authors: | John A Kairalla Keith E Muller Christopher S Coffey |
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| Institution: | 1. Department of Health Outcomes and Policy , College of Medicine, University of Florida , Gainesville, Florida, USA jak@biostat.ufl.edu;3. Department of Health Outcomes and Policy , College of Medicine, University of Florida , Gainesville, Florida, USA;4. Department of Biostatistics, School of Public Health , University of Iowa , Iowa City, Iowa, 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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| Keywords: | Adaptive designs Power Sample size re-estimation |
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