Abstract Details
Activity Number:
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458
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Type:
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Contributed
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Date/Time:
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Wednesday, August 6, 2014 : 8:30 AM to 10:20 AM
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Sponsor:
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Biopharmaceutical Section
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Abstract #313717
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View Presentation
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Title:
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Sample Size Calculation for Before-After Experiments with Partially Overlapping Cohorts
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Author(s):
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Song Zhang*+ and Jing Cao and Chul Ahn
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Companies:
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University of Texas Southwestern Medical Center and Southern Methodist University and University of Texas Southwestern Medical Center
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Keywords:
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GEE ;
Sample Size ;
before-after
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Abstract:
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We investigate sample size calculation for before-after experiments where the out- come of interest is binary and the enrolled subjects contribute a mixed type of data: some subjects contribute complete pairs of before- and after-intervention outcomes, while some subjects contribute incomplete data (before-intervention only or after- intervention only). We treat the incomplete observations as missing data in a general- ized linear model and the GEE approach is employed to derive a closed form sample size formula. The impacts of various designing factors are appropriately accounted for in the sample size formula, including intervention effect, baseline response rate, within-subject correlation, and distribution of missing values in the before- and after- intervention periods. We conduct simulation studies to demonstrate that the proposed sample size maintain the nominal power and type I error under a wide spectrum of trial configurations. A real application example is presented.
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Authors who are presenting talks have a * after their name.
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