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Edexcel S2 - 27th June 2016 AM

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Reply 720

Mattematics

Original post by fefssdf

thats exactly what I did !

The expected value of A = the expected value of Pi * R^2.

So it's Pi * E(R^2) rather than Pi times (E(R))^2.

Reply 721

Jellymath

Original post by iipebblesii

I got this too :frown:

Essentially A is not modelled by a continuous uniform distribution so you can't use it. Instead you need to use the formula in the formula book

(edited 7 years ago)

Reply 722

iMacJack

Original post by iipebblesii

I got this too :frown:

ImageUploadedByStudent Room1467022055.777196.jpg

HOW TO FIND E(A)

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Reply 723

1144297

Original post by hwilkoo

Can someone please explain E(A), as i got it to equal 49pi.

E(R) = (9+5)/2
E(R) = 7

E(A) = pi * 7^2
E(A) = 49pi

A = pi*R^2
E(A) = E(pi*R^2)
E(A) = pi*E(R^2)

so you had to work out Var(R) ( I think it was 4/3 or something?), and E(R) (7), and then use Var(R) = E(R^2) - E(R)^2, so E(R^2) = Var(R) + E(R)^2 = 4/3 + 49 = 151/3. So E(A) = piE(R^2) = 151pi/3 = 158.1.

Reply 724

justalawyer1998

Original post by fefssdf

it will drop down this year - I would say 62 maybe even 60 for an A as this was SO much harder than the 2015 paper

No way, this was easier than most simple because there were 2 long 'prove that' questions so people will get those. It'll be standard boundaries at the least

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Reply 725

hwilkoo

Original post by Mattematics

The expected value of A = the expected value of Pi * R^2.

So it's Pi * E(R^2) rather than Pi times (E(R))^2.

Thought that could be the case! Thanks

Reply 726

fefssdf

Original post by Supermanxxxxxx

For the 8 marker I got n=87 but I think I messed up when hiding the quadratic how many marks do you think Tisi Weill be

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i messed this up as well - I got like n=62 lol - you should get like 5/8 if you got up to making a quadratic tbh

That was horrible!

Original post by iMacJack

HOW TO FIND E(A)

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i did it by integration but fair enough

Reply 729

Piran.V

Original post by M3WIZARD

Question 1a) U = 1.44 Var(x) = 1.44 (3 Marks)b) U was approximately Variance (1 Mark)c) I – 0.251 II – 0.777 (4 Marks)d) 0.1378 (3 Marks)e) 0.152 (3 Marks) (Might be 0.132 – Rushed this onmy copy of answers) Question 2a) N=60 (2 Marks)b) I – 0.0133 II -0.0159 (5 Marks)c) 0.2396>0.01 Keep H0 (5 Marks)Question 3a) f(x) = ¼ 5=<R=<9 , 0 otherwise (1 Marks)b) 0.5 (1 Marks)c) 158.13 (4 Marks)Question 4a) Show that (6 Marks)b) K = 1/9 (4 Marks)Question 5 N = 225(I applied continuity correction – I honestly didn’t know if I should) (8Marks)Question 6a) 9 samples (2 Marks)b) 4 = ¼ , 5 = 3/10 , 6= 29/100 , 7 = 3/25, 8 =1/25 (5 Marks)c) N=57 (3 Marks)Question 7a) 1.2 (4 Marks)b) 0.24 (4 Marks)c) 0.325 (3 Marks)d) £41.88 (2 Marks)e) Shouldn’t remove staples (2 Marks) I’m not claiming these are all right – let me know J These are what I wrote

Got the same except the mean for the first one was 1.41.

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Reply 730

fefssdf

Original post by Nikhilm

No way, this was easier than most simple because there were 2 long 'prove that' questions so people will get those. It'll be standard boundaries at the least

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really... well are you suggesting it will be higher than 67 for an A cause that seems very unlikely...

Reply 731

mangoli

Went alright but was nothing like the past papers. Got stuck on finding k for 20 minutes and decided to move on, how did you guys do it? I got k = 1/(a+21) and couldnt hew another equation in a from it

Reply 732

Bill262626

Original post by hwilkoo

Can someone please explain E(A), as i got it to equal 49pi.

E(R) = (9+5)/2
E(R) = 7

E(A) = pi * 7^2
E(A) = 49pi

Same here..?

Reply 733

MathsFanatic!

Original post by iMacJack

HOW TO FIND E(A)

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Original post by ThatPerson2

Thanks guys, i get it now :smile:

Reply 734

Piers456

Original post by exclamationmark

How many marks was it to find the sample distribution of the other means?

I think 5 marks

Reply 735

kieran1119

I thought it was an ok paper and I didn't revise anything until half an hour before the exam and I'd like to think I got a safe B but I feel screwed for D2 tomorrow