Magenta96
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It's Q2iv on this link:

http://www.mei.org.uk/files/papers/s106ju_wu2y.pdf

In the previous parts I calculated in a venn diagram:
P(AnB) = 0.3
P(A) = 0.4
P(B) = 0.2
P(A'nB') = 0.1

By comparing P(B|A) with P(B), explain why Isobel should ask her parents to not attend. The answer is she scores better when her parents aren't there but when I compare P(B|A) which is 3/7 given in the q with P(B) which is 0.2 from my diagram, P(B|A) has the higher value suggesting her parents SHOULD attend so I'm confused.
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ghostwalker
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(Original post by Magenta96)
It's Q2iv on this link:

http://www.mei.org.uk/files/papers/s106ju_wu2y.pdf

In the previous parts I calculated in a venn diagram:
P(AnB) = 0.3
P(A) = 0.4
P(B) = 0.2
P(A'nB') = 0.1
How did you work out P(A) and P(B) there, as I don't agree with them?

You're actually told P(A) = 0.7
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Magenta96
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(Original post by ghostwalker)
How did you work out P(A) and P(B) there, as I don't agree with them?

You're actually told P(A) = 0.7
If you scroll down to the markscheme answer to 2ii, it shows a venn diagram and the P of just event A occurring is 0.4 as so I used that, I wasn't sure whether to use the P(A) from the venn diagram or the P(A) given in the question, why can't you use the one in the venn diagram by the way?
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ghostwalker
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(Original post by Magenta96)
If you scroll down to the markscheme answer to 2ii, it shows a venn diagram and the P of just event A occurring is 0.4 as so I used that, I wasn't sure whether to use the P(A) from the venn diagram or the P(A) given in the question, why can't you use the one in the venn diagram by the way?
The 0.4 in the Venn diagram refers to P(AnB'); this together with P(AnB) gives you P(A)

If you see something that's confusing, or doesn't seem right, either you're not understanding correctly, or there is an error in the question/markscheme.
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