Figure 1.

The problem of distinguishing between sequences. (a) An investigator contemplating the problem of distinguishing between sequences from the gut of Equus asinus and the volar forearm of humans. (b) Our solution; guess the effect size based on the effect sizes reported in published studies; perform simulations based on these effect sizes as shown in Figure 2, and then acquire sufficient sequences to resolve microbial community differences of the expected magnitude. (c) When comparing the Equus asinus gut (white point) to human forearms (red and green points represent left and right arms, respectively), 100 or even 10 sequences per sample provide sufficient resolution, but one sequence per sample does not.