1. In the first column in Excel, create column for Pr(B) -- this probability denotes the fraction of the general population that has antibodies. The first entry in this column is 0 and increase this value by .01 in successive rows until you reach 1.00. That is, the entries in the first column are 0, .01, .02, .03, ..., .99, 1.00.

2. In the second column in Excel, use Bayes Theorem to compute Pr(B|A) for all of the rows in the first column.

4. What is the probability that a person truly has antibodies given that a test shows the person has antibodies when

5% of the population has antibodies ____________?

10% of the population has antibodies ___________?

20% of the population has antibodies ___________?

40% of the population has antibodies ___________?

80% of the population has antibodies ___________?

5. Redo everything above but with sensitivity of .90 and specificity of .80. Put your work in the third and fourth columns in Excel and draw a new graph. Now, what is the probability that a person truly has antibodies given that a test shows the person has antibodies when

5% of the population has antibodies ____________?

10% of the population has antibodies ___________?

20% of the population has antibodies ___________?

40% of the population has antibodies ___________?

80% of the population has antibodies ___________?

Highlight the appropriate rows in Excel in light blue that answer the foregoing questions.