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. 2021 Dec 7;118(49):e2105254118.
doi: 10.1073/pnas.2105254118.

Fragility indices for only sufficiently likely modifications

Benjamin R Baer  1 , Mario Gaudino  2 , Mary Charlson  3 , Stephen E Fremes  4   5 , Martin T Wells  6   3
Affiliations

Fragility indices for only sufficiently likely modifications

Benjamin R Baer et al. Proc Natl Acad Sci U S A. .

Abstract

The fragility index is a clinically meaningful metric based on modifying patient outcomes that is increasingly used to interpret the robustness of clinical trial results. The fragility index relies on a concept that explores alternative realizations of the same clinical trial by modifying patient measurements. In this article, we propose to generalize the fragility index to a family of fragility indices called the incidence fragility indices that permit only outcome modifications that are sufficiently likely and provide an exact algorithm to calculate the incidence fragility indices. Additionally, we introduce a far-reaching generalization of the fragility index to any data type and explain how to permit only sufficiently likely modifications for nondichotomous outcomes. All of the proposed methodologies follow the fragility index concept.

Keywords: P value; evidence measure; fragility index; interpretability; statistical significance.

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Conflict of interest statement

The authors declare no competing interest.

Figures

Fig. 1.
Fig. 1.
Visualizations of the incidence fragility indices. Top Left, Top Right, and Bottom Left and Bottom Right correspond to Tables 5, 8, and 9 (top two rows and bottom two rows), respectively.
Fig. 2.
Fig. 2.
An illustration of four possible intervals that could be returned by the sufficiently likely construction of the outcome modifier relying on a normal distribution, for varying levels of confidence.
Fig. 3.
Fig. 3.
The generalized fragility indices for the t test indexed by the sufficiently likely threshold q.
See this image and copyright information in PMC

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