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    a fair coin is tosses repeatedly untill a head appears or 3 tosses have been made. The random variable T represents the number of tosses.

    A) show that P(T=2) = 1/4

    i have no idea how to answer this question i am absolutely confused. Any help would be apreciated thank you.
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    (Original post by sonic23)
    a fair coin is tosses repeatedly untill a head appears or 3 tosses have been made. The random variable T represents the number of tosses.

    A) show that P(T=2) = 1/4

    i have no idea how to answer this question i am absolutely confused. Any help would be apreciated thank you.
    A head appearing has a probability of 1/2
    Therefore, if T = 2, it has been rolled twice.

    Therefore, the probability a head will show after two tosses is 1/2 x 1/2 = 1/4

    I think that's right anyway.. Was never that good at stats but got an A
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    Thank you would tht be sufficient?
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    (Original post by Danielisew)
    A head appearing has a probability of 1/2
    Therefore, if T = 2, it has been rolled twice.

    Therefore, the probability a head will show after two tosses is 1/2 x 1/2 = 1/4

    I think that's right anyway.. Was never that good at stats but got an A
    I don't think this is right..
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    what ive written is :

    the only way in which 2 tosses can be made is if the first toss is not a head and the second toss is a head which is :

    1/2 x 1/2 = 1/4

    is tht ryt?
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    (Original post by sonic23)
    what ive written is :

    the only way in which 2 tosses can be made is if the first toss is not a head and the second toss is a head which is :

    1/2 x 1/2 = 1/4

    is tht ryt?
    hmm...i guess. my bad.
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    damn ryt
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    I found probability the hardest topic in S1, so don't worry because it can only get easier.. never understood probability apart from Venn diagrams really.

    In the real test, I got most of the probability right but lost 4 marks from it and then another 7/8 marks elsewhere, which gave me 85/100 - exactly what I predicted.
 
 
 
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