Table 2.
Findings from a hypothetical prevalence study of 20,000 persons.
| Exposed | Nonexposed | Ratio | |
|---|---|---|---|
| Cases | 909 (a) | 476 (b) | |
| Noncases | 9,091 (c) | 9,524 (d) | |
| Total population | 10,000 (N1) | 10,000 (N0) | |
| Prevalence | 0.0909 (P1) | 0.0476 (P0) | 1.91 |
| Prevalence odds | 0.1000 (O1) | 0.0500 (O0) | 2.00 |
Data are derived from Table 1 using Equation 2 based on the assumptions that, for both populations, the incidence rate and population size are constant over time, that the average duration of disease is 5 years, and that there is no migration of people with the disease into or out of the population.