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# Edexcel S2 - 27th June 2016 AM

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1. (Original post by kieran1119)
You get 555-2p=7sqrtp and if you square all of that then you got 4p^2 -2269p + 555^2 =0 and then if you solve it using the quadratic function you get two answers 225 and something else with a point 25 in and as you were finding n it had to be a whole number so 225 was the answer
Ah thank you, sorry, but how was the 2n derived? As I thought 1.75 (z value) = (55.5 - n) / (0.16n)^0.5
2. For question 7d I got 41.875 but then for some stupid reason rounded it to 41.82 so will I lose the mark because I rounded wrong? Will this affect me getting the marks in the second part? Thanks
3. 55.5-0.2n / (0.16n)^0.5 = 1.75
55.5-0.2n = 0.4*1.75n^0.5
3080.25-0.04n^2 = 0.49n
308025 - 4n^2 = 49n
4n^2+49n - 308025 = 0
.....
....
.... n = 82. something or 66. something
how did people get 225?
4. what was that hypothesis testing question i think it was the last part of question 2 or 3
5. I just put n =225 because in all questions I done before that were similar, they always squared the positive root
6. (Original post by NamelessPersona)
If you square both sides you treat it as a bracket
how many marks will i lose?
7. (Original post by KFC_Fleshlight)
55.5-0.2n / (0.16n)^0.5 = 1.75
55.5-0.2n = 0.4*1.75n^0.5
3080.25-0.04n^2 = 0.49n
308025 - 4n^2 = 49n
4n^2+49n - 308025 = 0
.....
....
.... n = 82. something or 66. something
how did people get 225?
would be root 0.16n not squared
8. can anyone remember the question for Q2 ??
9. (Original post by gameofthrones1)
how many marks will i lose?
I would say you would get at least 4, an M1 for using normal approx, an A1 for half cc, and an M1 and A1 for getting to 55.5-0.2n = 1.75*sqrt(0.16n)
10. How were you meant to do the last two questions on the paper?
11. (Original post by bulkybros100)
How were you meant to do the last two questions on the paper?
Use E(x) for a discrete distribution as sum of xf(x) and you get around 41.875 I think

Edit: E(x) = 50(27/40) + 25(13/40) = 41.875

you would then go on to say that if he sold n bags he would expect 41.875n pounds, but if he removed staples he would get 0.8n*50=40n.
As 41.875>40, he should not remove staples.
12. (Original post by iMacJack)
F(3)=1
F(2)=0

Then simultaneous

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(Original post by Yua)
I done it by integrating and making it equal 1, so working out the area under the graph

then F(3) =1

then simultaneous
****, im an idiot
Thanks anyway lads
13. (Original post by NamelessPersona)
Use E(x) for a discrete distribution as sum of xf(x) and you get around 41.875 I think
Do you think I would lose a mark for getting 41.875 then accidentally rounding this to 41.82? Thanks
14. (Original post by bulkybros100)
How were you meant to do the last two questions on the paper?
(1-0.325)50 + 0.325(25) = E(X) = 41.88

if he removes staples then because 20% less bins you do 0.8(50) = 40

40<41.88

so he should not remove staples as he'd make less money
15. (Original post by TheSammy2010)
My answers, idk if they are right

Q1,
Mean= 1.41
Variance= 1.4419
Probabilities; 0.7769, 0.1378, 0.1516

Q2,
N=60
0.0133
0.0159
Do not reject Ho (using binomial tables)

Q3,
0.75
151π/3

Q4,
K=1/9

Q5,
N=225

Q6,
P(M=5)= 0.3
P(M=6)= 0.29
P(M=7)= 0.12

N=11

Q7,

Mean= 1.2
Var= 1.92
P(X>3)= 0.3250
£41.88 per bin

He shouldn't as the mean profit of bins would be £40
Question 2 the hypothesis test was 0.2236 which is more than 0.01 therefore accept null hypothesis

Question 3 it was 0.5 not 0.75

Question 4 n was 57

Rest are right

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16. (Original post by economicss)
Do you think I would lose a mark for getting 41.875 then accidentally rounding this to 41.82? Thanks
I wouldn't think so but I'm not entirely sure

Edit: oops misread what you rounded to, yeah I think you would lose a mark
17. What we thinking on grade boundaries then?
18. (Original post by Rey Mysterio)
What we thinking on grade boundaries then?
65= A
19. (Original post by Rey Mysterio)
What we thinking on grade boundaries then?
Pretty high, probably similar to last year
20. (Original post by TheBigBo)
It was n and sqrt(n) so the roots of the quadratic are equal to the sqrt of n and then you square the positive one as sqrt(x)≥0
Omg I spent so long on that question thinking that n couldn't possibly be 15!!! Forgot that it was root(n) 😂

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