Biostatistics and Epidemiology

(25 points)

1. Define sensitivity and specificity.

2. 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.

3. Define positive predictive value (PPV) and negative predictive value (NPV).

4. An epidemiologist in Saudi Arabia wants to study the efficacy of iron supplementation for the prevention of HIV infection. He wants to make sure that only subjects who are free of HIV infection are enrolled in his trial. Based on the outcome of the test, he decides who could participate in his iron supplementation trail. For this purpose, it is very important that diagnostic test has high…………… ……..