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Unread 4 Jun 2003, 12:44   #1
Tobe
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maths help
ta

Anne plays a game, 6 sided fair die if she rolls

1,2,3 she loses £10
4,5 she wins £x
6 she wins £2x

show that the e(X) of annes profit is £(2/3x-5) in a single game
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Unread 4 Jun 2003, 12:46   #2
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I can't believe I've failed so much in maths.

I haven't got a clue what the answer is, but I know this is pish easy.
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Unread 4 Jun 2003, 12:48   #3
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i know but the p(b|a) ones always confuse me
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Unread 4 Jun 2003, 12:54   #4
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Well there are 10 with nuts, of which 6 have hard centres, so I'd guess the probability is 3/5.

And I'd guess e(x) is 7.5, although the question doesn't appear to make sense, as x could be anything...

By the way, Statistics is evil.
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Unread 4 Jun 2003, 12:55   #5
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Re: maths help
Quote:
Originally posted by Tobe

13 hard centre, of these 13, 6 contain nuts

7 soft centre, of these 7, 4 contain nuts

find p of it having a hard centre given it contains a nut
isn't this the same as "contains a nut AND has a hard center" ?


In which case it would be 10/20 * 6/10

where 10/20 is the chance of finding a nut and 6/10 is the chance of finding a hard center.

Or if you already HAVE the information that it does indeed contain a nut then it would just be 6/10.

i might be very wrong though.
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Unread 4 Jun 2003, 12:55   #6
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Re: maths help
Quote:
Originally posted by Tobe


20 chocolates

13 hard centre, of these 13, 6 contain nuts

7 soft centre, of these 7, 4 contain nuts

find p of it having a hard centre given it contains a nut
it contains a nut... so that means it can only be one of 10... um... the way im thinking it should just be 60% or whatever. but thats far too easy...

poo

but i dont see why the ones that dont have nuts in should be counted at all... as you have already taken one that contains a nut, unless i misunderstand you.

cant you just ignore the 3 nutless soft and 7 nutless hards completely? leaving you with 6 nutted hard and 4 nutted soft? IT ALREADY SAID IT CONTAINED A NUT...

oh bah

im sure im wrong, because like i said its far too easy. but 60% heh.

(P.S i got an E in a level maths... so there are some more points stacked against me)
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Unread 4 Jun 2003, 12:55   #7
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Quote:
Originally posted by Proteus
Well there are 10 with nuts, of which 6 have hard centres, so I'd guess the probability is 3/5.

And I'd guess e(x) is 7.5, although the question doesn't appear to make sense, as x could be anything...

By the way, Statistics is evil.

Luckily this isn't statistics.
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Unread 4 Jun 2003, 12:57   #8
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Quote:
Originally posted by menth0l
Luckily this isn't statistics.
It's probability, so of course it's statistics.
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Unread 4 Jun 2003, 12:58   #9
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i hate given that questions although i see its 3/5 for q 2
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Unread 4 Jun 2003, 12:59   #10
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Quote:
Originally posted by Proteus
It's probability, so of course it's statistics.

probability is an area of mathematics.

so is statistics.

this is probability.

this is not statistics.
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Unread 4 Jun 2003, 13:03   #11
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Quote:
Originally posted by menth0l
probability is an area of mathematics.

so is statistics.

this is probability.

this is not statistics.
The exam boards would disagree with you.
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Unread 4 Jun 2003, 13:06   #12
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Quote:
Originally posted by Proteus
The exam boards would disagree with you.
the exam board calls the paper probability and statistics 1
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Unread 4 Jun 2003, 13:08   #13
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Quote:
Originally posted by Proteus

Statistics applies some bits of probability. Does not mean that all probability is automatically statistics.


Screw the exam boards, i work with statistics for a living
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Unread 4 Jun 2003, 13:09   #14
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Quote:
Originally posted by menth0l
Statistics applies some bits of probability. Does not mean that all probability is automatically statistics.


Screw the exam boards, i work with statistics for a living
I did this kind of probability in a statistics exam.
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Unread 4 Jun 2003, 13:13   #15
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Quote:
Originally posted by Proteus
I did this kind of probability in a statistics exam.

Yes, because obviously basic probability is something you need to know to be able to do statistics.


Jesus ****ing christ.


I'm through arguing about this.
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Unread 4 Jun 2003, 13:16   #16
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Re: maths help
Quote:
Originally posted by Tobe
ta

Anne plays a game, 6 sided fair die if she rolls

1,2,3 she loses £10
4,5 she wins £x
6 she wins £2x

show that the e(X) of annes profit is £(2/3x-5) in a single game
(-10 * (1/2)) + (x * (1/3)) + (2x * (1/6)) =e(x)

= -5 + (x/3) + (x/3)

= (2x/3) - 5

If you are going to use brackets at least use them correctly Tobe as the answer you ask for is wrong
Last edited by MrPeach; 4 Jun 2003 at 13:22.
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Unread 4 Jun 2003, 13:17   #17
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Quote:
Originally posted by Tobe
the exam board calls the paper probability and statistics 1
Not my exam board.
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