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# Edexcel S2 - 27th June 2016 AM

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Why bother with a post grad? Are they even worth it? Have your say! 26-10-2016
• View Poll Results: How did you find the Edexcel S2 exam?
Very hard
145
14.71%
Hard
331
33.57%
Normal
293
29.72%
Easy
152
15.42%
Very easy
65
6.59%

1. (Original post by iMacJack)
Normal Approx I did this can someone tell me what I'd lose

X-B(n,0.2)

Goes to

Y-N(0.2n,0.16n)

P(Y>55) = P(Y>55.5) = P(Z>(55.5-n)/0.4rootn)) = 0.0401 (whatever t was) Then I did p(z<=(55.5-n)/0.4rootn) = 0.9699

therefore (55.5-n)/0.4rootn = 1.75

I then solved a quadratic and got the value of N as 51. The slip I made was misreading my own writing and putting 55.5-n instead of 55.5-0.2n

How many dropped??

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probably 2-3 marks
2. (Original post by target21859)
Worrying won't help but the wait to find out what I got is killing me
Same!
I forgot to square 15 to get 225 and i messed up on the circle question, everything else was pretty good I reckon ive got around 67-70 dependant.
I really need A* after screwing up M2 despite getting 95 last year on D2
3. (Original post by river222)
Same!
I forgot to square 15 to get 225 and i messed up on the circle question, everything else was pretty good I reckon ive got around 67-70 dependant.
I really need A* after screwing up M2 despite getting 95 last year on D2
Yeah I need A* in FM. My exams went so well last year but this year I really screwed up. I know I can do it but not under exam conditions. I always make really stupid mistakes.
4. (Original post by ISAAQAHELP)
oh didn't see that prob one accuracy mark. they might not notice like i did but i am doing 2 stuff at once so i wasn;'t paying attention
Yeah... there's no chance of them not noticing haha

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5. (Original post by ISAAQAHELP)
none the accept both decimal and percentage
0.1 isn't the correct significance level so he would lose a mark at least. it was 1% not 10%
6. i did q5 by trial and error so how many marks would i get? i also correctly changed the binomial to normal and did a continuity correction but couldn't get the correct answer unless i did trial and error?
7. (Original post by target21859)
only 80?
Well, S2 is sort of unpredictable. That mark would easily get you a solid A with 84+ UMS on IAL June 14 or June 15, but would be a high B on UK 15 or IAL Jan 16... I say relax until the grade boundaries are released - even then, you could still be severely underestimating yourself!
8. Does anyone know if @kprime2 is DOIN model answers

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9. (Original post by igotohaggerston)
How many marks was the P(7<R<10) question
What was the answer to this question????!
10. (Original post by iMacJack)
Does anyone know if @kprime2 is DOIN model answers

Posted from TSR Mobile
He said he would in another thread, probably tomorrow.
11. (Original post by Ayman!)
Well, S2 is sort of unpredictable. That mark would easily get you a solid A with 84+ UMS on IAL June 14 or June 15, but would be a high B on UK 15 or IAL Jan 16... I say relax until the grade boundaries are released - even then, you could still be severely underestimating yourself!
12. (Original post by Ayman!)
Well, S2 is sort of unpredictable. That mark would easily get you a solid A with 84+ UMS on IAL June 14 or June 15, but would be a high B on UK 15 or IAL Jan 16... I say relax until the grade boundaries are released - even then, you could still be severely underestimating yourself!
I did calculate the absolute minimum I could get. I think I could get up to 69 (that would be great). Last year I was a lot more confident about what I was going to get. Got 198/200 in C3 and C4 so no problem there for A* in normal maths and I thought FM was in the bag as well...
13. (Original post by Dentistry101)
What was the answer to this question????!
I just did the area so (10-7)*probability. I can't rightly remember what the probability was, maybe 1/4? If so it would just be 3/4.
14. 0.5
15. (Original post by igotohaggerston)
0.5
Was that a reply to me??
16. (Original post by Jack_Linaker)
I just did the area so (10-7)*probability. I can't rightly remember what the probability was, maybe 1/4? If so it would just be 3/4.

But the distribution was U~[5,9] so would it not be 2 x 0.25??
17. The distribution was [5,9] so it would've been 0.25*(9-7)=0.5
18. (Original post by ISAAQAHELP)
THIS IS THE QUESTION FOR THE normal APPROX.

X-B(N,0.2) USING NORMAL APPROX AND GIVEN THAT P(X>55)=0.0401
FIND N

X-B[N,0.2]= W-N[X,Y"] X IS MEAN Y" IS VARIANCE " MEANS SQUARED

P(X>55)=P[W>55.5)=P(Z>([55.5-X]/Y)=0.0401

P(Z<([55.5-X]/Y)=1-0.0401=0.9599

USING TABLE

(55.5-X)/Y=1.75
55.5-X=1.75Y
1.75Y+X=55.5 NOW USING THE BINOMIAL PARAMETERS
WE CAN FIND Y AND X IN TERMS OF N
X=0.2N
Y"=0.2*0.8N Y"=0.16N Y=0.4N! WHERE !=SQUARE ROOT
SO 1.75(0.4N!)+0.2N =55.5
0.7N!+0.2N=55.5
0.2N+0.7N!-55.5=0 NOW SOLVE THIS USING QUADRATIC FORMULA
YOU GET N!=15 OR (-18.5)
SO N = 225 OR 342.25 BUT WE ARE DEALING STUDENTS
SO N=225 ONLY
don't KNOW WHY PEOPLE ARE GETTING 200

I know I did wrong. I used 55 not 55.5 , worked out 223 and 340. I didn't reject 340..... How many marks I will lost?
19. (Original post by Dentistry101)
But the distribution was U~[5,9] so would it not be 2 x 0.25??
God dammit you're right fml
20. Could someone link me the unofficial scheme?

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