Statistics question- EdExcel 2005 paper

There is a question on section b (question 8) about megan throwing darts at a dartboard.
I worked it out using the binomial distribution formula (ncr) and got 0.6484 or something.
However in the question, they say 'you pay use (p+q)^3 as' bla blah, and wondering what relevelance that has to the question- it didnt help me! does that mean the answer I have is wrong? thanks!

EDIT: Scroll down to my 3rd post for more :P

Reply 1

brimstone

7

Have you got a copy of that paper? I'd be interested to see it as that's the one I sat. :smile:

Reply 2

tiger_vio

OP

11

brimstone

Have you got a copy of that paper? I'd be interested to see it as that's the one I sat. :smile:

well my maths teacher just gave it to me- and i don't have a scanner to scan it in :frown:

it probably was your paper :smile:

Reply 3

brimstone

7

Aw

I was asking my Maths teacher for a copy of it since we did the blasted thing and I never got one :bawling:

Reply 4

tiger_vio

OP

11

brimstone

Aw

I was asking my Maths teacher for a copy of it since we did the blasted thing and I never got one :bawling:

aww that sucks! lmao
Well ive come to the conclusion that this exam wnats a different method (the cgp way).
Its nice that they give you the expansion of (p+q)^3- although i cant for the life of me work it out (i understand (p+q)^2 though!) but nevermind.
So if the formula is

p^3 + 3p^2q+3pq^2+q^3, do I just have to substitute p with 7/9, and q with 2/9? Or do I just change them to fractions or what? ahhh..

Reply 5

Eternity Forever

12

tiger_vio

There is a question on section b (question 8) about megan throwing darts at a dartboard.
I worked it out using the binomial distribution formula (ncr) and got 0.6484 or something.
However in the question, they say 'you pay use (p+q)^3 as' bla blah, and wondering what relevelance that has to the question- it didnt help me! does that mean the answer I have is wrong? thanks!

EDIT: Scroll down to my 3rd post for more :P

Megan throws darts at a target. She can hit the target with 7 out of 9 throws. Megan throws three darts.

Assuming a binomial distribution, work out the probability that she hits the target exactly twice. You may use (p+q)^3, which is equal to: p^3 +3p^2q+3pq^2+q^3.

Ok, firstly you need to know that p=success outcomes (7/9)and q=unsuccessful outcomes (2/9)

So, we are looking for the part of the formula where P is squared and that part can only be 3p^2q
Therefore: substituting the values we have; 3*7/9^2 *2/9
This then is equal to 98/243, which in decimal form is 0.403

Hope that helps.

Statistics question- EdExcel 2005 paper

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