Question

Erin's family had a 70% risk of heart attack, Erin took a 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%. The test predicted that Erin will not have a heart attack. What is the probability after the test was taken that she will have a heart attack?

I did 0.70 * 0.67 = 0.469 Not correct
Can someone show me the steps? please!

Answer 1

These are my choices
0.4051
0.5010
0.4653
I've tried multiplying, adding the two sums and dividding
I'm not getting it and those were the two ways I was shown unless I missed something???

Answer 2

@ganeshie8 do u have any idea?

Answer 3

you need to find : P("heart attack" | "test result is negative")

Answer 4

use bayee's theorem

Answer 5

Im getting this :
http://www.wolframalpha.com/input/?i=%280.7*0.33%29%2F%280.7*0.33+%2B+0.3*0.67%29

but its not there in ur options :/
@amistre64 @mathmale

Answer 6

@phi

Answer 7

@ganeshie8 I agree with your numbers. The best I can come up with is a typo in the question. The probability of *not* having an attack is 0.201/.432= 0.4653
i.e. 1 - 0.5747

Answer 8

I took a sceen shot of the question. I'm starting to think all my questions are faulty some how.

Answer 9

I tried the calculating the difference of the 33% but I didn't come up with any of those answers. Thanks anyways.

Answer 10

Can you ask your teacher about this question?
The answer is 0.5347 chance of having an attack given that the test says she would not
The prob is 0.4653 of not having an attack given the test says she would not.

Answer 11

thanks I will send her a message. This is the third question that was crazy wrong.