A rapid strep test is often given in a clinical setting so that, if needed, antibiotics can begin as soon as possible. Researchers at Cochrane.org evaluated the effectiveness of rapid strep tests and found that one type had a sensitivity (ability to correctly detect people with strep) of 85.4% and a specificity (ability to correctly identify people who do NOT have strep) of 95%
Fill in the following chart, assuming that you have a group of 10,000 people, 15% of whom actually have strep throat.
Patient is given a rapid strep test
Result is positive Result is negative totals
Has strep throat
Does not have strep
Totals 10,000
For a population of patients similar to those described in the stem of this problem, use the chart find each of the following probabilities. Write you answer as an abbreviated probability statement with your answer to four decimal places without using a percent symbol. For example, P(strep) = 0.15
A) The probability that a randomly chosen patient has strep throat and tests positive
B) The probability that a randomly chosen patient tests positive for strep throat.
C) The probability that a randomly chosen person actually has strep throat, given that they have tested positive.

[tex]\text{strep value} \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 1281\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 219 \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 1500 \\\\[/tex]

[tex]\text{not the strep value} \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 425 \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 8075 \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 8500 \\\\ \text{total} \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 1706 \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 8294 \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 10000 \\\\[/tex]

In point a:

[tex]P( \text{step and positive test}) = \frac{1281}{10000}=0.1281[/tex]

In point b:

[tex]P(\text{positive test}) =\frac{1706}{10000} =0.1706[/tex]

In point c:

[tex]P \text{(strep | positive test)} =\frac{1281}{1706} =0.7509[/tex]