negative – adj. in a medical test, negative means the person being tested does not have a disease or condition
sample – n. a small amount of something that gives you information about the thing it was taken from
confidence – n. a feeling of being sure in one's ability to do something
positive – adj. in a medical test, positive means the person being tested has a disease or condition
quarantine – n. to keep (a person or animal) away from others to prevent a disease from spreading