Table 8.

Bayesian inference of a SARS-CoV-2 test on a person taken from a social group with high prevalence and no symptoms. The final, posterior probability of SARS-CoV-2 infection is 17–19% for a negative test result, and 67–93% for a positive test result, depending if one assumes a pessimistic or optimistic false positive rate, respectively.

Description	Posterior	Likelihood	Prior	Marginal
Baseline / prior			0.666
+ No symptoms	0.361	0.246	0.666	0.450
+ Negative test (P)	0.190	0.347	0.361	0.658
+ Negative test (O)	0.167	0.347	0.361	0.658
Baseline / prior			0.666
+ No symptoms	0.361	0.246	0.666	0.450
+ Positive test (P)	0.689	0.653	0.361	0.342
+ Positive test (O)	0.934	0.653	0.361	0.252