Fig. 1.

Conceptual illustration of the difference between a descriptive and an analytical analysis. A depicts a descriptive study, where both ratios are calculated off of the same denominator, and thus there is really only one study population. No formal statistical testing is applicable between 57 versus 43%. B depicts an analytical study, where there are two different study populations (i.e., the 55% is calculated off of a different denominator as the 57%). In that case, formal statistical testing is applicable to compare 55 versus 57%. A P value not applicable to compare different parts of the same populations. B P value applicable for comparing parts of two populations