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S1 Paper need help on some questions!

Hey guys, so I have attached the paper and need help on the following questions:

2 iv)
3) ii) iii)
6) b)

Any help and methods would really be appreciated, thanks! :smile:
4732Jan11.pdf108.6KB
Reply 1
Avatar for Naomiimoan
Naomiimoan
3
Sorry I did s1 last year so I don't remember how to do 2 and 6 :s-smilie:
3)ii) the pmcc is greater than 0.9 showing that there is a very strong positive correlation.
iii)-you cannot make accurate assumptions based on extrapolated data (as there's solid evidence).
-there is only so much profit the company can make so his assumption may only be valid for a short period of time.
Reply 2
Avatar for Nator
Nator
OP
3
Original post by Naomiimoan
Sorry I did s1 last year so I don't remember how to do 2 and 6 :s-smilie:
3)ii) the pmcc is greater than 0.9 showing that there is a very strong positive correlation.
iii)-you cannot make accurate assumptions based on extrapolated data (as there's solid evidence).
-there is only so much profit the company can make so his assumption may only be valid for a short period of time.


Thanks for the response! :smile: And I understand no problem :wink: Anyone else know how to do the other 2 questions? :s-smilie:
Reply 3
Avatar for vc94
vc94
12
2iv) If X and Y are both ~Ge(0.2) we want P(X+Y=3)
= P(X=1 and Y=2) + P((X=2 and Y=1)

You can work out out each of these probabilities by multiplying since X and Y are independent.
Reply 4
Avatar for Nator
Nator
OP
3
Original post by vc94
2iv) If X and Y are both ~Ge(0.2) we want P(X+Y=3)
= P(X=1 and Y=2) + P((X=2 and Y=1)

You can work out out each of these probabilities by multiplying since X and Y are independent.


So the answer is 2 x 0.2 x (0.2 x 0.8) = 0.064? Also can 3 and 0 work or not?
Reply 5
Avatar for vc94
vc94
12
Original post by Nator
So the answer is 2 x 0.2 x (0.2 x 0.8) = 0.064? Also can 3 and 0 work or not?


Looks good.
The way you learnt geometric, isn't it defined for X=1,2,3.... i.e. excluding zero?
So you can't have 0 and 3.

Do you have an answer for 6b from the mark scheme? Want to check my answer.
Reply 6
Avatar for Nator
Nator
OP
3
Original post by vc94
Looks good.
The way you learnt geometric, isn't it defined for X=1,2,3.... i.e. excluding zero?
So you can't have 0 and 3.

Do you have an answer for 6b from the mark scheme? Want to check my answer.


Yeah it's what I was thinking, but could 0 be counted as the first fail i.e. 0.8?

And sorry I don't have the mark scheme, that's why I am asking people to see what answer's they get :tongue: Care to explain your technique for question 6b?
Reply 7
Avatar for vc94
vc94
12
Original post by Nator
Yeah it's what I was thinking, but could 0 be counted as the first fail i.e. 0.8?

And sorry I don't have the mark scheme, that's why I am asking people to see what answer's they get :tongue: Care to explain your technique for question 6b?


If you're using P(X=k) = (1-p)^(k-1) *p as your geometric model then you can't have X=0.

6b) First case: white "A" and grey "non-A".
If you have a white "A" then that leaves 4C2 choices for the other white cards.
If none of the grey cards are "A" then you have 9C4 choices.
Total of 756.

Second case: white non-A and grey A.
Count the choices using a similar method...
Reply 8
Avatar for Nator
Nator
OP
3
Original post by vc94
If you're using P(X=k) = (1-p)^(k-1) *p as your geometric model then you can't have X=0.

6b) First case: white "A" and grey "non-A".
If you have a white "A" then that leaves 4C2 choices for the other white cards.
If none of the grey cards are "A" then you have 9C4 choices.
Total of 756.

Second case: white non-A and grey A.
Count the choices using a similar method...


Second case: for white non-A you would have 4C3, and for grey A you would have 9C3.
Total of 336.

Now how do you use these results to convert this into a probability?
Reply 9
Avatar for Nator
Nator
OP
3
Would you then just do: (336 + 756) / 5C3 X 10C4 = 0.52? Is that the answer you got?
Reply 10
Avatar for vc94
vc94
12
756 + 336 = 1092 ways.
To get the probability, divide 1092 by answer to 6a.
Reply 11
Avatar for vc94
vc94
12
Original post by Nator
Would you then just do: (336 + 756) / 5C3 X 10C4 = 0.52? Is that the answer you got?


Looks good
Reply 12
Avatar for Nator
Nator
OP
3
Original post by vc94
Looks good


Awesome, rep for you good sir :smile:

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