Re: Specificity and sensitivity

On Sep 10, 4:44 pm, quebecs...@xxxxxxx wrote:
Dear forum

I am trying to answer questions regarding medical screening, and
medical testing.

My biostatistics professor asked the following two questions:

1/Specificity and sensitivity are really important for what kind of
study/test?

2/For what kind of study/test is it important to think about the
Positive Predictive Value (PPV) and Negative Predictive Value (NPV)?

I thought that sens/specificity was the analog of NPV/PPV. I need more
insight.

Can anybody help?

Many thanks for your help.

The population of individuals without disease is the focus of
specificity. It identifies the characteristic effectiveness of a test
to correctly identify those without disease.

The formula for specificity is (true negatives/ true negatives plus
false positives) X100

The population of individuals who have disease is the focus of
sensitivity. It is the capacity of a test in identifying individuals
with disease.

The formula for that is (true positives/ true positives plus false
negatives) X 100

The population of individuals with a positive test result is the focus
of positive predictive value and the negative predictive value are
those with a negative result that indicates the likelihood that a
negative test result identifies someone without disease.

Those are all the populations that they represent.


.