Covariate

On the basis of these analogies, any inference of a population structure driven by selective sweeps would require good longitudinal data from natural bacterial populations, as well as observations of episodic crashes in diversity causally associated with genetic changes and not associated with changes in ecological covariates.

Mahalanobis used a visual method of approximating the standard error of the income at all the fractiles of the covariate for the same graph by taking two independently selected "interpenetrating subsamples" and obtaining a graph for each of the subsamples besides the combined sample.