# computing sensitivity, specificity, Positive predictive value and Negative predictive values of the test for presence and absence of the disease

A cancer screening test is being applied in a population of 200 men who were also evaluated through the biopsy of tumor. 30 of the men were confirmed having cancer through biopsy. Out of these 30, 25 were also found to have cancer through the screening test. Screening test also found 15 cases to be having cancer but this was not confirmed by biopsy. Based on this information draw 2 x 2 table showing numbers in each of the 4 cells and compute sensitivity, specificity, Positive predictive value and Negative predictive values of the test for presence and absence of the disease.

In this case am wondering what is the true positive value. I think it is 25 since it was confirmed through two methods. But again the question mentions that 30 were confirmed. Now I wonder, is it 25 or 30. For false negative is it 5?

$$\begin{array}{|l|c|c|c|} \hline ~&+&-&~\\ \hline +&TP&FN&AP\\ \hline -&FP&TN&AN\\ \hline ~&PP&PN&ALL\\ \hline \end{array}$$
$$\begin{array}{|l|c|c|c|} \hline ~&+&-&~\\ \hline +&25&5&30\\ \hline -&15&155&170\\ \hline ~&40&160&200\\ \hline \end{array}$$