Refer to the table which summarizes the results of testing for a certain disease. $$\begin{array} { l | c c }
& \begin{array} { l }
\text { Positive } \
\text { Test Result }
\end{array} & \begin{array} { l }
\text { Negative } \
\text { Test Result }
\end{array} \
\hline \text { Subject has the disease } & 87 & 9 \
\text { Subject does not have the disease } & 27 & 312
\end{array}$$ 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) 0.028
B) 0.094
C) 0.221
D) 0.972

Question

Refer to the table which summarizes the results of testing for a certain disease. $$\begin{array} { l | c c } 
& \begin{array} { l } 
\text { Positive } \
\text { Test Result }
\end{array} & \begin{array} { l } 
\text { Negative } \
\text { Test Result }
\end{array} \
\hline \text { Subject has the disease } & 87 & 9 \
\text { Subject does not have the disease } & 27 & 312
\end{array}$$ 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) 0.028
B) 0.094
C) 0.221
D) 0.972

Quizplus · Accepted Answer

The probability that the subject has the disease given a negative test result is calculated as the number of true negatives divided by the total number of negative test results: 9 / (9 + 312) = 9 / 321 ≈ 0.028.

Refer to the Table Which Summarizes the Results of Testing