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# Edexcel S2 - 27th June 2016 AM Watch

• 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

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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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