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Probability questions
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Thimodya/Waspinator
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Admin- Admin
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Re: Probability questions
Thimodya/Waspinator Wed Jan 05, 2011 8:21 am
I think the answer is 6.5
because if the probability of obtaining A is 0.5 and obtaining B is 0.35 and the probability of obtaining neither's intersection is o.2
then 0.5 - 0.2 is 0.3 and 0.35- 0.2 is 0.15
and 0.15 + 0.5 is 0.65 and 0.3+0.35 is also 0.65...................right?
someone please help me this is confusing
because if the probability of obtaining A is 0.5 and obtaining B is 0.35 and the probability of obtaining neither's intersection is o.2
then 0.5 - 0.2 is 0.3 and 0.35- 0.2 is 0.15
and 0.15 + 0.5 is 0.65 and 0.3+0.35 is also 0.65...................right?
someone please help me this is confusing
Thimodya/Waspinator- Posts : 10
Points : 10
Join date : 2010-10-03
Re: Probability questions
Federico Fri Jan 07, 2011 9:09 pm
I think that it's 0.45.
I did the same thing as Timmy, but instead I added 0.3 to 0.15.
But it could be 0.2.
Neither's intersection is the middle bit, isn't it. So it would be 0.2
So confused
I did the same thing as Timmy, but instead I added 0.3 to 0.15.
But it could be 0.2.
Neither's intersection is the middle bit, isn't it. So it would be 0.2
So confused
Federico- Posts : 8
Points : 10
Join date : 2010-10-03
Re: Probability questions
fergus Sat Jan 08, 2011 1:22 am
freddy i dont think A'∩B' is the middle section. Mr safdar wouldnt give us a question with the answer writen in front of us.Federico wrote:I think that it's 0.45.
I did the same thing as Timmy, but instead I added 0.3 to 0.15.
But it could be 0.2.
Neither's intersection is the middle bit, isn't it. So it would be 0.2
So confused
im not too sure if 0.3 to 0.15s wrong though
so i also think its 0.45
the letters in bold give off a truth
fergus- Posts : 18
Points : 29
Join date : 2010-10-03
Age : 113 -
Re: Probability questions
Luka a.k.a GodOfRandom Sat Jan 08, 2011 2:03 am
fergus wrote:freddy i dont think A'∩B' is the middle section. Mr safdar wouldnt give us a question with the answer writen in front of us.Federico wrote:I think that it's 0.45.
I did the same thing as Timmy, but instead I added 0.3 to 0.15.
But it could be 0.2.
Neither's intersection is the middle bit, isn't it. So it would be 0.2
So confused
im not too sure if 0.3 to 0.15s wrong though
so i also think its 0.45
not bad fergus but thats not a good hidden message and i think that A'∩B' is anything that is not A intersects with anything that is not B so the entire outside of both circles
we want to find where A and B both occur so what we want is the probability of A∩B however where i am having trouble finding that.
the letters in bold give off a truth
Luka a.k.a GodOfRandom- Admin
- Posts : 13
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Join date : 2010-10-03
Re: Probability questions
Jihye Choi Sat Jan 08, 2011 6:01 am
I think the answer is 0.05
because [p(A'∩B') = 0.2] is the probability of obtaining neither's intersection,
and we want to find p(A and B), middle section.
p(A) = 0.5 , p(B) = 0.35 , p(A'∩B') = 0.2 , and I think E = 1
E - p(A'∩B') = p(A∪B)
1 - 0.2 = 0.8 -----------------> so, p(A∪B) = 0.8
p(A∪B) = p(A) + p(B) - p(A∩B)
0.8 = 0.5 + 0.35 - p(A∩B)
∴ p(A∩B) = 0.5 + 0.35 - 0.8 = 0.05
because [p(A'∩B') = 0.2] is the probability of obtaining neither's intersection,
and we want to find p(A and B), middle section.
p(A) = 0.5 , p(B) = 0.35 , p(A'∩B') = 0.2 , and I think E = 1
E - p(A'∩B') = p(A∪B)
1 - 0.2 = 0.8 -----------------> so, p(A∪B) = 0.8
p(A∪B) = p(A) + p(B) - p(A∩B)
0.8 = 0.5 + 0.35 - p(A∩B)
∴ p(A∩B) = 0.5 + 0.35 - 0.8 = 0.05
Jihye Choi- Posts : 2
Points : 2
Join date : 2010-10-11
Well done
Admin Sun Jan 09, 2011 1:51 am
Well done Rachel. 0.05 is correct.
If you want to find the answer in terms of areas- the area inside the circles has to be 0.8. P(a)+P(b)=0.85 therefore we have 0.05 extra or counted twice.
If you want to find the answer in terms of areas- the area inside the circles has to be 0.8. P(a)+P(b)=0.85 therefore we have 0.05 extra or counted twice.
Admin- Admin
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