Translations:Advanced Field Epi:Manual 2 - Diagnostic Tests/150/en: Perbedaan revisi
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− | <nowiki>The above example illustrates one potential problem with Rogan and Gladen formula, which is that in some circumstances negative estimates can be produced. However, a negative (<0) prevalence is clearly impossible, so for this scenario the assumptions about sensitivity and specificity must be incorrect. For example, if specificity was 90% (0.9), and you tested 150 </nowiki>animals, you would expect to have 0.1*150 or on average about 15 false positive results (even in an uninfected population). Therefore if only 4 positives were recorded, the specificity of the test must be much higher than 90% (a minimum estimate would be to assume all of the positives are false positives, so that specificity = 1 | + | <nowiki>The above example illustrates one potential problem with Rogan and Gladen formula, which is that in some circumstances negative estimates can be produced. However, a negative (<0) prevalence is clearly impossible, so for this scenario the assumptions about sensitivity and specificity must be incorrect. For example, if specificity was 90% (0.9), and you tested 150 </nowiki>animals, you would expect to have 0.1*150 or on average about 15 false positive results (even in an uninfected population). Therefore if only 4 positives were recorded, the specificity of the test must be much higher than 90% (a minimum estimate would be to assume all of the positives are false positives, so that specificity = 1 - apparent prevalence = 1 - 4% or 96%). |
Revisi terkini pada 10 Mei 2015 14.26
The above example illustrates one potential problem with Rogan and Gladen formula, which is that in some circumstances negative estimates can be produced. However, a negative (<0) prevalence is clearly impossible, so for this scenario the assumptions about sensitivity and specificity must be incorrect. For example, if specificity was 90% (0.9), and you tested 150 animals, you would expect to have 0.1*150 or on average about 15 false positive results (even in an uninfected population). Therefore if only 4 positives were recorded, the specificity of the test must be much higher than 90% (a minimum estimate would be to assume all of the positives are false positives, so that specificity = 1 - apparent prevalence = 1 - 4% or 96%).