Fay and Wu's H

Fay and Wu's H is a statistical test created by and named after two researchers Justin Fay and Chung-I Wu. The purpose of the test is to distinguish between a DNA sequence evolving randomly ("neutrally") and one evolving under positive selection. This test is an advancement over Tajima's D, which is used to differentiate neutrally evolving sequences from those evolving non-randomly (through directional selection or balancing selection, demographic expansion or contraction or genetic hitchhiking). Fay and Wu's H is frequently used to identify sequences which have experienced selective sweeps in their evolutionary history.