101 research outputs found
The development of thirty self-administering and self-scoring elaborative thinking exercises
Thesis (Ed.M.)--Boston Universit
MedZIM: Mediation analysis for Zero-Inflated Mediators with applications to microbiome data
The human microbiome can contribute to the pathogenesis of many complex
diseases such as cancer and Alzheimer's disease by mediating disease-leading
causal pathways. However, standard mediation analysis is not adequate in the
context of microbiome data due to the excessive number of zero values in the
data. Zero-valued sequencing reads, commonly observed in microbiome studies,
arise for technical and/or biological reasons. Mediation analysis approaches
for analyzing zero-inflated mediators are still lacking largely because of
challenges raised by the zero-inflated data structure: (a) disentangling the
mediation effect induced by the point mass at zero; and (b) identifying the
observed zero-valued data points that are actually not zero (i.e., false
zeros). We develop a novel mediation analysis method under the
potential-outcomes framework to fill this gap. We show that the mediation
effect of the microbiome can be decomposed into two components that are
inherent to the two-part nature of zero-inflated distributions. The first
component corresponds to the mediation effect attributable to a unit-change
over the positive relative abundance and the second component corresponds to
the mediation effect attributable to discrete binary change of the mediator
from zero to a non-zero state. With probabilistic models to account for
observing zeros, we also address the challenge with false zeros. A
comprehensive simulation study and the applications in two real microbiome
studies demonstrate that our approach outperforms existing mediation analysis
approaches.Comment: Corresponding: Zhigang L
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