If a woman takes an early pregnancy test, she will either test positive, meaning that the test says she is pregnant, or test negative, meaning that the test says she is not pregnant. Suppose that if a woman really is pregnant, there is a 98% chance that she will test positive. Also, suppose that if a woman really is not pregnant there is a 99% chance that she will test negative.

*suppose that 1,000 women take early pregnancy tests and that 100 of them really are pregnant. What is the probability that a randomly chosen woman from this group will test positive?

Question

If a woman takes an early pregnancy test, she will either test positive, meaning that the test says she is pregnant, or test negative, meaning that the test says she is not pregnant. Suppose that if a woman really is pregnant, there is a 98% chance that she will test positive. Also, suppose that if a woman really is not pregnant there is a 99% chance that she will test negative.

*suppose that 1,000 women take early pregnancy tests and that 100 of them really are pregnant. What is the probability that a randomly chosen woman from this group will test positive?

anonymous · Answer

10% of 1000

anonymous · Answer

10% of 1000, so would it just be 100/1000

slinley · Answer

100/1000

slinley · Answer

Yass
 @jerrijones

kropot72 · Answer

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If you look at the probability tree above you will see that the probability that a randomly chosen woman from this group will test positive is given by:
0.098 + 0.009 = 0.107

kropot72 · Answer

|dw:1412036683931:dw|

anonymous · Answer

thanks @kropot72, I did the exact same tree diagram I just wasn't sure exactly what to add or multiply

kropot72 · Answer

You're welcome. I hope it is clear now :)