Algebra 2 Probability

Question

It is estimated that 4% of people will get strep throat. Of the people with strep throat, the test for infection will give a

positive reading 97% of the time. Given someone does not have strep throat, the test will give a negative reading 92%

of the time. Given someone gets a positive reading, what is the probability they have strep throat?

Round to the nearest thousandth if necessary.

Answer 1

P( people will get strep throat)= 4% = 4/100

people with strep throat infection positive time = 97% = 97/100

P( positive reading and strep throat) = 4/100 × 97/100 = 388/100 = 0·0388

0·0388≈0·039 (nearest thousandth).