Table 2 Sample size calculation for prevalence (source Openepi.com)
Calculations of sample size estimates 95% limits of confidence | ||||||||
|---|---|---|---|---|---|---|---|---|
sample size (number of patients) | ||||||||
600 | 1100 | 1500 | 1750 | 2200 | 3500 | 5000 | 10,000 | |
Anticipated prevalence of resistant bacteria | 95% limits of confidence (+/− % of prevalence) | |||||||
0.5% | +/− 0.5 | +/− 0.4 | +/− 0.35 | +/− 0.30 | +/− 0.25 | +/− 0.20 | +/− 0.14 | +/− 0.03 |
1% | +/− 0.8 | +/− 0.55 | +/− 0.45 | +/− 0.40 | +/− 0.35 | +/− 0.30 | +/− 0.20 | +/− 0.05 |
10% | +/− 2.5 | +/− 1.75 | +/− 1.4 | +/− 1.25 | +/− 1.2 | +/− 1.0 | +/− 0.6 | +/− 0.2 |
25% | +/− 3.5 | +/− 2.5 | +/− 2.0 | +/− 1.75 | +/− 1.70 | +/− 1.45 | +/− 0.9 | +/− 0.2 |
Example: at a prevalence of for instance MRSA of 0.5% the 95% limits of confidence with a sample size of 1.100 patient is +/0.4%, which means that the prevalence with 95% certainty is from 0.1–0.9%. | ||||||||