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Table 2 Minimum sample sizes required to estimate freedom from Johne’s Disease (JD) at the herd level, using an imperfect test and adjusting for a finite population calculated using the AusVet EpiTool Epidemiological calculator (URL: http://epitools.ausvet.com.au)

From: Use of a voluntary testing program to study the spatial epidemiology of Johne’s disease affecting dairy herds in Minnesota: a cross sectional study

Herd size (number of cows)

Sample sizea

5–20

N/A (Recommendation: Same as herd size)

21–25

20

26–40

24

41–55

25

56–65

26

66–80

27

81–95

28

96–100

29

101–250

30

> 251

31

  1. aAssumptions: a) design prevalence, i.e. expected within herd prevalence =10%, b) sensitivity of the diagnostic test of 52%, and c) expected number of test infected cows in a herd is a product of herd size and the design prevalence
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BMC Veterinary Research

ISSN: 1746-6148

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