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Instructions: enter the number of cases in the diseased group that test positive (a) and negative (b); and the number of cases in the non-diseased group that test positive (c) and negative (d).

Next click the Test button.

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TestPresentn AbsentnTotal
PositiveTrue Positive a=
False Positive c=
a + c
NegativeFalse Negative b=
True Negative d=
b + d
Total a + b   c + d  

Disease prevalence

If the ratio of cases in the Disease Present and Disease Absent groups
does not reflect the disease prevalence, enter:

disease prevalence (%):


Statistic Value 95% CI
Positive Likelihood Ratio    
Negative Likelihood Ratio    
Disease prevalence    
Positive Predictive Value (*)    
Negative Predictive Value (*)    
Accuracy (*)    

(*) These values are dependent on disease prevalence.

See Help for computational details and interpretation.

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