Step 1 :The problem is asking for the probability that a subject has the disease given that the test result is negative. This is a conditional probability problem.
Step 2 :We can use the formula for conditional probability to solve this problem. The formula is \(P(A|B) = \frac{P(A \cap B)}{P(B)}\). In this case, event A is the subject has the disease and event B is the test result is negative.
Step 3 :We can find \(P(A \cap B)\) by looking at the number of subjects who have the disease and tested negative, which is 9.
Step 4 :We can find \(P(B)\) by looking at the total number of subjects who tested negative, which is 321.
Step 5 :Substitute these values into the formula, we get \(P(A|B) = \frac{9}{321} = 0.028037383177570093\).
Step 6 :Rounding to three decimal places, the final answer is \(\boxed{0.028}\).