Wiki Sumber Informasi iSIKHNAS

• Individual and group level test characteristics (sensitivity and specificity) are not equivalent.
• The number of animals to be tested in the group (sample size) is relatively independent of group size except for small groups (<~1000) or where sample size is more than about 10% of the group size. Alternative methods are available for small populations or where sample size is large relative to group size.
• The number of animals required to be tested in the group depends much more on individual animal specificity than it does on sensitivity.
• The number of animals to be tested in the group is linearly and inversely related to the expected prevalence of infected animals in the group.
• As the required level of statistical confidence increases, so the required sample size increases. The usual level is 95%. If this is increased to 99%, there is an approximate increase of 50% in the required sample size. For a reduction from 95% to 90% confidence, there is a decrease in sample size by 25%.
• As the sample size increases, group level sensitivity increases.
• As the number of animals used to classify the group as positive is increased, there is a corresponding increase in specificity.
• As group level sensitivity increases, group level specificity decreases.
• When specificity = 100% at the individual animal level, all uninfected groups are correctly classified i.e. group level specificity also equals 100%.