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Select the correct answer.
On discovering that her family had a 70% risk of heart attack, Erin took treadmill test to check her own potential of having a heart attack. The
doctors told her that the reliability of the stress test is 67%. What is the probability that Erin will not have a heart attack and the test predicts that
she will?
© A. 0.099
© B. 0.201
© C. 0.231
0.469


Sagot :

Answer:

A. 0.099

Step-by-step explanation:

Conditional Probability

We use the conditional probability formula to solve this question. It is

[tex]P(B|A) = \frac{P(A \cap B)}{P(A)}[/tex]

In which

P(B|A) is the probability of event B happening, given that A happened.

[tex]P(A \cap B)[/tex] is the probability of both A and B happening.

P(A) is the probability of A happening.

In this question:

Event A: She does not have a heart attack.

Event B: tests predicts that she will have a heart attack

The doctors told her that the reliability of the stress test is 67%.

This means that there is a 100 - 67 = 33% of not having a heart attack if the test predicts she will have a heart attack, so:

[tex]P(B|A) = 0.33[/tex]

70% risk of heart attack

So 100 - 70 = 30% probability of not having a heart attack, which means that [tex]P(A) = 0.3[/tex]

What is the probability that Erin will not have a heart attack and the test predicts that she will?

[tex]P(B|A) = \frac{P(A \cap B)}{P(A)}[/tex]

[tex]P(A \cap B) = P(B|A)*P(A) = 0.33*0.3 = 0.099[/tex]

The correct answer is given by option A.