G6PD and COVID-19: Researchers used the Kruskal–Wallis H-test as an alternative to a one-way analysis of variance (one-way ANOVA) because the number of measurements in the G6PD + COVID-19 group ranged from 4 to 18 measurements and due to the existence of a considerable disparity in numbers between the three research groups, as well as the absence of a random selection process for group membership.