The Witness test for feline leukemia has a 92.9% sensitivity and 96.5% specificity. Assume for this question that 2% of
cats in a population actually have the disease.
a) Draw a tree diagram representing this situation.
b) Calculate the probabilities for each of the following test results: true positive, false negative, true negative,
false positive.
c) What is the probability that a cat who tests positive truly does have leukemia? “Fun” fact: this probability is
called the positive predictive value.
d) What is the probability that a cat who tests negative truly does not have leukemia? This quantity is called the
negative predictive value.

Round probabilities/proportions to three decimal places at the end of your
calculations.