Often people are confused about the precision that should be used when estimating sample size for prevalence studies. Some guidance here
From: Sample size calculation for prevalence studies using Scalex and ScalaR calculators
| Expected Prevalence | Recommended Precision | ||||
| Large Scale | Small Scale | Preliminary Study | Remark | ||
| 1 | 10 to 90% | 2 ~ 3% | 4 ~ 5% | > 5% | |
| 2 | < 10% | 0.25*EP | 0.50*EP | > 0.50*EP | Cannot be equal to EP or larger |
| e.g. 4% | 1% | 2% | > 2% | Cannot be 4% or larger | |
| 3 | > 90% | 0.25*(100-EP) | 0.5*(100-EP) | > 0.5*(100-EP) | Cannot be (100-EP) or larger |
| e.g. 95% | 1.25% | 2.5% | > 2.5% | Cannot be 5% or larger | |
EP Expected Prevalence in percent
Reference
https://bmcmedresmethodol.biomedcentral.com/articles/10.1186/s12874-022-01694-7/tables/2