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 Post subject: Probability question....
PostPosted: Sun Jul 08, 2012 1:48 pm 
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Joined: Tue Mar 08, 2011 9:16 am
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Would really like to understand this one....

For which of these can you work out the probability exactly?

A) It will rain tomorrow when class B go on a school trip.
B) Mr. Wood will pass his driving test
C) Stuart will miss the 8.30 am bus to school
D) Emily will throw heads when she tosses a coin
E) Amy will come third in a swimming competition

?????


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PostPosted: Sun Jul 08, 2012 1:52 pm 
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D is the only one where the outcomes are equally likely.

Two outomes Head or tail - probability of a Head is 1/2.


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PostPosted: Sun Jul 08, 2012 1:56 pm 
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Guest55 wrote:
D is the only one where the outcomes are equally likely.

Two outomes Head or tail - probability of a Head is 1/2.


Thanks Guest55
What about passing/failing driving test isn't that 1/2 ( pass or fail )
Is this a straight forward one, have really struggled on it....


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PostPosted: Sun Jul 08, 2012 2:07 pm 
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countrymum wrote:

B) Mr. Wood will pass his driving test

D) Emily will throw heads when she tosses a coin




Both these are 50/50


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PostPosted: Sun Jul 08, 2012 2:17 pm 
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I think that for the probability to be calculated you have to know that each outcome is equally likely . heads or tails is equally likely but passing or failing a test may not be equally likely


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PostPosted: Sun Jul 08, 2012 2:18 pm 
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Passing and failing a driving test are not equally likely - I think it varies from test centre to test centre and a driver could be appalling.

Theoretical probability only applies where 'skill' is not part of the picture - spinning a coin, throwing a die, etc.

Playing football depends on the teams playing - the weather depends on the time of year and the country.


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PostPosted: Sun Jul 08, 2012 2:19 pm 
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Location: East Kent
Manana wrote:
countrymum wrote:

B) Mr. Wood will pass his driving test

D) Emily will throw heads when she tosses a coin




Both these are 50/50


I guess someone is only likely to take their driving test if they think the odds are they are likely to pass - a coin toss has no element of skill (in that practice can have any outcome on the result you are likely to get)


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PostPosted: Sun Jul 08, 2012 2:27 pm 
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Guest55 wrote:
Passing and failing a driving test are not equally likely - I think it varies from test centre to test centre and a driver could be appalling.

Theoretical probability only applies where 'skill' is not part of the picture - spinning a coin, throwing a die, etc.

Playing football depends on the teams playing - the weather depends on the time of year and the country.


Thanks everyone and guest55, thanks so much for that. It has all clicked and I get it now! Kind of thinking out of the box and taking many outside influences into account ( like for eg the weatherman mayhave got it wrong or like you say he may a rubbish driver etc etc )

Yes the answer is indeed D! If I get stuck again can I come back :lol:
You are all masters of maths :D


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PostPosted: Sun Jul 08, 2012 2:49 pm 
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I should hope so as I spend my life teaching it!


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