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Epidmeiology - Specificity and Sensitivity

The sensitivity and specificity of a new test are 60% and 70%, respectively. Three hundred people are screened at a clinic during the first year the new test is implemented. Assume the true prevalence of disease among clinic attendees is 10%. Set up the 2x2 table to calculate positive predictive value. (Hint: Use prevalence for determining marginal total of subjects who have the disease, TP+FN. Use this information and formulas for sensitivity and specificity to determine TP, FN, FP and TN).

Q.1 What is the predictive value of a positive test?
Q.2 And the number of true negative?

Solution Preview

Hi there,

I hope the following explanation helps you understand the concepts required to answer this question. All the best with your epidemiology course!

The table that is referenced in the question looks like this:

True Disease Status
Test Result Present Not Present

Positive TP FP

Negative FN TN

Where TP is true positive, FP is false positive, FN is false negative and TN is true negative

To determine the values that will go into the table, we need to use the true prevalence data as well as the sample ...