# A quick probability qWatch

Announcements
Thread starter 6 years ago
#1
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.
0
6 years ago
#2
(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
0
Thread starter 6 years ago
#3
(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?
0
6 years ago
#4
(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.
0
X

new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### University open days

• The University of Law
The Bar Series: Applications and Interviews - London Bloomsbury campus Postgraduate
Thu, 17 Oct '19
• Cardiff Metropolitan University
Undergraduate Open Day - Llandaff Campus Undergraduate
Sat, 19 Oct '19
• Coventry University
Sat, 19 Oct '19

### Poll

Join the discussion

#### Why wouldn't you turn to teachers if you were being bullied?

They might tell my parents (10)
6.45%
They might tell the bully (16)
10.32%
I don't think they'd understand (28)
18.06%
It might lead to more bullying (58)
37.42%
There's nothing they could do (43)
27.74%

View All
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.