the key was to add cell A + cell A,B+B,C+C,D+D,to make one 2x2 table.

If you follow exposed with disease,exposed without disease,unexposed with diseased,and unexposed without disease,each one should be added together young and old.

Then you do a/ a+b and divide it by c/c+d to find the RR

2. Suppose that your company has just developed a new screening test for a disease and you are in charge of testing its validity and feasibility. You decide to evaluate the test on 1000 individuals and compare the results of the new test to the gold standard. You know the prevalence of disease in your population is 30%. The screening test gave a positive result for 292 individuals. 285 of these individuals actually had the disease on the basis of the gold standard determination. a. Fill in all cells of the two by two table. (6 points) b. Calculate the sensitivity of the new screening test. (4 points) c. Interpret the results of sensitivity calculation in one sentence. (2 points) d. Calculate the specificity of the new screening test. (4 points) e. Interpret the results of specificity calculation in one sentence. (2 points) f. Calculate the predictive value of a positive test. (4 points) g. Interpret the results of the predictive value positive calculation in one sentence. (2 points) h. What would happen to the predictive value positive if this test were administered in a population with a disease prevalence of 1% instead of 30%? (Note that the sensitivity and specificity of the test remain the same.) Would it remain the same? Increase? Decrease