A correlation between a binary and the continuous variable can
be measured statically by the point-biserial correlation coefficient,
rpb. In this case, rpb described the association between the binary
variable, prevalence of Salmonella positive samples, and the
continuous variable, the count of enterococci in the samples. The
rpb was found to be 0.11, which was statistically significantly
different from zero (n ¼ 4421; P < 0.001). As shown in Fig. 2,
prevalence of Salmonella increased significantly with increasing
concentrations of enterococci in the samples. Salmonella was
detected in 1.1% (95-% C.I.: 0.8e1.5%) of samples with less than
100 CFU/g of enterococci, in 3.3% (95-% C.I.: 2.4e4.5%) of samples
harbouring from 100 to 10,000 CFU/g of enterococci and in 16% (95-
% C.I.: 4.6e36%) of samples with 10,000 CFU/g or more of
enterococci.