The table below shows the predicted testing outcome for a disease that affects [tex]2\%[/tex] of a population and has a [tex]90\%[/tex] accuracy rate.

\begin{tabular}{lccc}
& Positive Test & Negative Test & Total \\
Has Disease & 18 & 2 & 20 \\
Does Not Have Disease & 98 & 882 & 980 \\
Total & 116 & 884 & 1000
\end{tabular}

Given you received a positive test, which of the following represents the probability that you do not have the disease?

A. [tex]84.5\%[/tex]

B. [tex]99.8\%[/tex]

C. [tex]15.5\%[/tex]

D. [tex]0.2\%[/tex]



Answer :

First, let's analyze the given table to understand the data provided:

[tex]\[ \begin{array}{lccc} & \text{Positive Test} & \text{Negative Test} & \text{Total} \\ \text{Has Disease} & 18 & 2 & 20 \\ \text{Does Not Have Disease} & 98 & 882 & 980 \\ \text{Total} & 116 & 884 & 1000 \\ \end{array} \][/tex]

We need to determine the probability that a person does not have the disease given that they received a positive test result.

### Steps to Solve:

1. Identify the relevant numbers:
- Number of positive test results = 116 (from the total positive tests column).
- Number of positive test results where the person does not have the disease = 98 (from the "Does Not Have Disease" row under the positive test column).

2. Calculate the probability:
- The probability of not having the disease given a positive test result is the ratio of the number of positive tests where the person does not have the disease to the total number of positive tests.
[tex]\[ P(\text{No Disease} | \text{Positive Test}) = \frac{\text{Number of Positive Tests with No Disease}}{\text{Total Number of Positive Tests}} = \frac{98}{116} \][/tex]

3. Convert the probability to a percentage:
- To convert this probability to a percentage, multiply by 100.
[tex]\[ P(\text{No Disease} | \text{Positive Test}) \times 100 = \left(\frac{98}{116}\right) \times 100 \][/tex]

4. Determine the final value:
- Given our calculations:
[tex]\[ \frac{98}{116} \approx 0.8448275862068966 \][/tex]
- Converting this to a percentage:
[tex]\[ 0.8448275862068966 \times 100 \approx 84.48275862068965 \% \][/tex]

### Conclusion:

The probability that a person does not have the disease given that they received a positive test result is approximately [tex]\( 84.5\% \)[/tex].

So, the correct answer is:
[tex]\[ \boxed{84.5\%} \][/tex]