The Student Room Group
Reply 1
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 :smile:
Reply 2
Thank you would tht be sufficient?
Reply 3
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 :smile:


I don't think this is right..
Reply 4
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?
Reply 5
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.
Reply 6
damn ryt
Reply 7
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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