3 Life Technologies | Animal Health
Sample size
Sample sizes may vary based on in-herd prevalence level of a disease, the tested
disease itself, confidence level of the outcome, the requested test method, and the
purpose of the sampling.
Number of samples needed for detection of disease
i.e., at least one infected animal has tested positive
Group size
% diseased animals within a group
5% 10% 20%
Number of samples (95% confidence level)
100 44 25 13
200 50 26 13
300 53 27 13
750 57 28 13
3,000 58 29 13
Number of samples needed for determination of disease prevalence
i.e., when an estimation of prevalence has to be made by the vet; confirmation will then be done by testing a particular
sample size
Group size
Estimated
prevalence
Precision (95% confidence level)
±5% ±10% ±20%
200 10% 82 30 10
200 20% 111 47 15
200 50% 132 65 22
500 10% 109 35 10
500 20% 165 55 15
500 50% 217 81 24
3,000 10% 138 35 10
3,000 20% 246 61 15
3,000 50% 341 96 24
