### Start Here: Instructions for Herpes Test

There are several different viruses that can cause painful blisters, including herpes and others. There are medicines that are helpful against herpes. However, if the other virus is mistakenly diagnosed, the medicine could cause complications, so it is useful to test for herpes.

Suppose the older, less expensive test correctly gives a “positive” test result in 70% of the cases of people with herpes and gives a false “positive” result in 30% of the cases of people without herpes. Suppose that there is a new expensive test for herpes simplex that correctly gives a “positive” test result in 90% of the cases of people with herpes and gives a false “positive” result in 10% of the cases of people without herpes.

Based on a patient's age and medical history the rate of herpes varies. One group has a base rate of 20% and the other has an 80% rate of having herpes without taking the test.

Scroll down and look at the trials below. Your task is to put the information together in each case to estimate the probability that the person actually has herpes, based on their medical history and up to two diagnostic tests, summarized at the left.

#### Warmup Trials Medical Decisions

W1.
Med. history: 20% rate of herpes
new test: herpes negative

W2.
Med. history: 80% rate of herpes
old test herpes positive
(no other tests given)

W3.
Med. history: 20% rate of herpes
(no other tests given)

W4.
Med. history: 80% rate of herpes
old test herpes positive
new test: herpes negative

1.
Med. history: 80% rate of herpes
old test herpes positive
new test: herpes positive

2.
Med. history: 20% rate of herpes
(no other tests given)

3.
Med. history: 80% rate of herpes
old test: herpes negative
new test: herpes positive

4.
Med. history: 20% rate of herpes
old test: herpes negative
new test: herpes negative

5.
Med. history: 80% rate of herpes
old test herpes positive
(no other tests given)

6.
Med. history: 80% rate of herpes
old test herpes positive
new test: herpes negative

7.
Med. history: 20% rate of herpes
old test herpes positive
new test: herpes positive

8.
Med. history: 80% rate of herpes
old test: herpes negative
new test: herpes negative

9.
Med. history: 20% rate of herpes
new test: herpes negative

10.
Med. history: 20% rate of herpes
old test herpes positive
new test: herpes negative

11.
Med. history: 20% rate of herpes
old test herpes positive
(no other tests given)

12.
Med. history: 20% rate of herpes
old test: herpes negative
(no other tests given)

13.
Med. history: 80% rate of herpes
(no other tests given)

14.
Med. history: 20% rate of herpes
new test: herpes positive

15.
Med. history: 80% rate of herpes
old test: herpes negative
(no other tests given)

16.
Med. history: 80% rate of herpes
new test: herpes negative

17.
Med. history: 20% rate of herpes
old test: herpes negative
new test: herpes positive

18.
Med. history: 80% rate of herpes
new test: herpes positive

19. What is your age? years.
20. Gender: Are you Male or Female?
Female
Male

21. How many years of Education have you completed? Put 12 for High School Diploma
Put 16 for college diploma (bachelor's degree).
put 20 for doctorate degree (Ph.D., M.D., etc).
Education:
22. Nationality (country of birth):