Refer to the table which summarizes the results of testing for a certain disease $\begin{array}{l|cc}
& \begin{array}{l}
\text { Positive } \
\text { Test Result }
\end{array} & \begin{array}{l}
\text { Negative } \
\text { Test Result }
\end{array} \
\hline \text { Subject has the disease } & 87 & 9 \
\text { Subject does not have the disease } & 27 & 312
\end{array}$

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) $0.094$
B) $0.028$
C) $0.972$
D) $0.221$

Question

Refer to the table which summarizes the results of testing for a certain disease $\begin{array}{l|cc} 
& \begin{array}{l}
\text { Positive } \
\text { Test Result }
\end{array} & \begin{array}{l}
\text { Negative } \
\text { Test Result }
\end{array} \
\hline \text { Subject has the disease } & 87 & 9 \
\text { Subject does not have the disease } & 27 & 312
\end{array}$

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) $0.094$
B) $0.028$
C) $0.972$
D) $0.221$

Quizplus · Accepted Answer

The probability that a subject has the disease given a negative test result is calculated using the formula for conditional probability: P(A|B) = P(A and B) / P(B). Here, A is the event that the subject has the disease, and B is the event of a negative test result. From the table, 9 subjects have the disease and tested negative, and there are a total of 321 negative results (9 + 312). Therefore, the probability is 9/321 = 0.028.

Refer to the Table Which Summarizes the Results of Testing