Fig. 2

Venn diagram illustrating the classification of outlets as true positives (TP), false positives (FP) and false negatives (FN). The left-hand oval represents all outlets identified in the audits, and the right-hand oval represents all outlets identified by the secondary data (POI or FSA). The region of overlap depicts outlets that were identified in both the audits and the dataset. The figure also shows the equations used to calculate sensitivity statistics and positive predictive values (PPV) and their respective odds, where P(X) represents the probability of event X