1.A new screening for breast cancer is being tested on 1,200 volunteers. Among the volunteers, 20% of them have breast cancer. The sensitivity is 78% and the specificity is 90% for the screening. What is the number of true positives that were screen positives? What is the number of true negatives that were screen negative? [4 points]

True positives: __________________

True negatives: __________________

2.. In question 1 above, what are the numbers of false positives and false negatives? [4 points]

False positives: __________________

False negatives: __________________

3. In a screening test for Chlamydia, the sensitivity is 83% and specificity is 50%. A total of 800 subjects were screened, of whom 90 actually had Chlamydia (confirmed through follow-up testing). Calculate and interpret the Positive and Negative predictive values. [4 points]

Positive predictive value: __________ Interpretation: ____________________________

Negative predictive value: __________Interpretation: ____________________________

4. Refer to the figure below: