The motivation for this post was also recent question on twitter asking how one might approach the analysis of an AB/BA crossover study when the goal is to estimate the difference in the relative abundance of microbial taxa under treatments A and B.
One of the most common questions we get from investigators at the Microbial Metagenomics Analysis Center (MMAC) is how many samples should I collect for my study? Even once we have a clearly stated and testable hypothesis, this is not always easy, since sample size calculations for microbiome studies are typically not amenable to closed form solutions (i.
I recently analyzed some data from an experiment with a pre-post study design where our estimands of interest were the baseline adjusted mean difference in Shannon diversity and species differential abundance between arms at post-treatment.
I was thinking recently about the performance of linear models for differential abundance testing in microbiome studies (see here for an example) despite the sparse, extremely non-normal, and compositional nature of mixed microbial community taxonomic profiles.
BACKGROUND: A dietary assessment instrument designed for use in a nationally representative pediatric population was required to examine associations between calcium intake and bone mineral accrual in a large, multicenter study. OBJECTIVE: To …
BACKGROUND: Little is known regarding the number of 24-hour recalls required to rank-order children and adolescents on usual intake for diet-disease studies. OBJECTIVE: To determine the within- to between-individual variance ratios and number of …