Refer to the table which summarizes the results of testing for a certain disease. $\begin{array}{lcc}
& {\text { Positive Test Negative Test }} \
\text { Subject has the disease } & \text { Result } & \text { Result } \
\text { Subject does not have the disease } & 87 & 9 \
& 27 & 312
\end{array}$ A test subject is randomly selected and tested for the disease. What is the probability the subject has the disease given that the test result is negative.
A) 0.972
B) 0.094
C) 0.028
D) 0.221

Question

Refer to the table which summarizes the results of testing for a certain disease. $\begin{array}{lcc} 
& {\text { Positive Test Negative Test }} \
\text { Subject has the disease } & \text { Result } & \text { Result } \
\text { Subject does not have the disease } & 87 & 9 \
& 27 & 312
\end{array}$ A test subject is randomly selected and tested for the disease. What is the probability the subject has the disease given that the test result is negative.
A) 0.972
B) 0.094
C) 0.028
D) 0.221

Quizplus · Accepted Answer

The probability that the subject has the disease given a negative test result is calculated using the formula for conditional probability: P(Disease | Negative) = P(Disease and Negative) / P(Negative). From the table, P(Disease and Negative) = 9, and P(Negative) = 9 + 312 = 321. Thus, the probability is 9/321 = 0.028.

Refer to the Table Which Summarizes the Results of Testing