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S2 Edexcel Thursday 24th May AM - PAPER & SOLUTIONS IN FIRST POST

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Original post by TheAdrianoo789
To your first bit, who knows. Maybe you'll get a few.

To your second bit, yeah that makes sense altho it was symmetrical so you could just have done 2(P(X<1.5)) i think... but it doesn't matter :P


Hopefully.. I didnt even think of that so much wasted time:angry:
So how did u do in this paper, and what do u need?
Reply 301
What is the full mark for the sampling distribution of range question?
I just didn't understand what was "sampling distribution of range" and I just found the sampling distribution of outcomes lol
Any luck getting any marks for that question? :frown:
Really want an A* in S2... seems like the range question ruins it
Original post by TheAdrianoo789
To your first bit, who knows. Maybe you'll get a few.

To your second bit, yeah that makes sense altho it was symmetrical so you could just have done 2(P(X<1.5)) i think... but it doesn't matter :P


Hopefully.. I didnt even think of that so much wasted time:angry:
So how did u do in this paper, and what do u need?
can anyone remember the number of marks allocated for the last part of the Questions (3) and (4)??
How did you lot do "Write down E(X)."?

I had to use integration, which probably wasn't the way they wanted.
Reply 305
Original post by js12

0.2277 (i think this is wrong from what others have said)


Why wrong?I got that too.
Reply 306
Original post by OneMorePanda
How did you lot do "Write down E(X)."?

I had to use integration, which probably wasn't the way they wanted.


I did the intergration way too, and the same for Var(X) [ex^2 -e(x)^2], but you could have done a+b/2 or (b-a)^2/12 They both give the same answers, so I think theyll accept :smile:
Reply 307
here are my problems,almost heated discussions

1.For distribution,I wrote (111,112,211,121,etc..)then I got weird answers like w/8000 x/8000 y/8000 z/8000..anyone? ALMOST everyone in my class did this way.I actually dunno what did 'range' mean in that question.Anyone?

2.For 8,I used X~B(10,0.6).For(b),I used p who don't ask for water (0.4) to calculate,then I got 0.9536 maybe.Anyone?

3.For a question about blah blah half minute,I did F(2.5)-F(1.5) but my mate used 0-1.5 and 4-2.5 .I think he is probably right.
Reply 308
isnt anyone going to put the answers up..!
Original post by @Sean43
I did the intergration way too, and the same for Var(X) [ex^2 -e(x)^2], but you could have done a+b/2 or (b-a)^2/12 They both give the same answers, so I think theyll accept :smile:


It wasn't a continuous uniform distribution though, was it? I'm sure it had an term in it.
Reply 310
Original post by maxthepax
got n=36 :frown: literally did every past paper since 2008 and this was by FARRRrr the hardest 1. Sampling distributions of the range are not even in the text book!!!!

My teachers (who had the paper afterwards) said they were unsure as to whether the last question was x-b(10,0.6) or x-Po(6) so i reckon they are both going to be right (I did binomial btw)

I did binomial, because p was not small, 0.6 is quite a large probability and so poisson would give a not so great approximation
Reply 311
please do put up the solution asap. dying to see it!!
Reply 312
Original post by Adam_x
here are my problems,almost heated discussions

1.For distribution,I wrote (111,112,211,121,etc..)then I got weird answers like w/8000 x/8000 y/8000 z/8000..anyone? ALMOST everyone in my class did this way.I actually dunno what did 'range' mean in that question.Anyone?

2.For 8,I used X~B(10,0.6).For(b),I used p who don't ask for water (0.4) to calculate,then I got 0.9536 maybe.Anyone?

3.For a question about blah blah half minute,I did F(2.5)-F(1.5) but my mate used 0-1.5 and 4-2.5 .I think he is probably right.

I have a lousy memory, so I've already forgotten most of the paper. However, using fractions for sampling question (your 1) was the best way to go I think and I certainly remember getting 8000 in the denominator. If your numerators added up to 8000, then you're sorted.

Did something similar for your 2, but the last part of that question was tricky.

For your 3, I thought it was a cdf? So integrating f(x) between 1.5 and 2.5 would give the probability, iirc.
Reply 313
Original post by justreadthebooks
OH MY GOD just thinking about that exam makes me feel ill. i did a sampling distribution for the combinations so like 111,112,121,122,221 etc instead cause that's how i interpreted "the range of values" ...oh god :| method marks maybe????


That's exactly what I did! The "range" completely went over my head, even though I've prcticed finding the mean, median and model of it before! I'm so angry with myself. I can't see us getting more than 1 or 2 marks tbh because all I think I got right was the list of possible outcomes. *sighs*
Reply 314
When can we view the solution???? Its killin me :mad
Urgggh, you would not believe how annoying this paper was. The last question!!! I put fliplflopping 34 because I forgot to add 1 to it at the end....grrrrrrrrrrrrrrrrrrrr. I think I guessed how to sampling distribution correctly though. Phewww.
Reply 316
When are the solutions coming up? I got n = 35 at first, then scribbled it out and did it a different way! So so angry
It was all going so well until I got to 5(c), then it became a f-ckery.

Range, really?!
Fricking a five-rowed CDF, really?!
Reply 318
Original post by grazie
I have a lousy memory, so I've already forgotten most of the paper. However, using fractions for sampling question (your 1) was the best way to go I think and I certainly remember getting 8000 in the denominator. If your numerators added up to 8000, then you're sorted.

Did something similar for your 2, but the last part of that question was tricky.

For your 3, I thought it was a cdf? So integrating f(x) between 1.5 and 2.5 would give the probability, iirc.


But for distribution,as I've seen above,many got answer like 0:0.3175 1:0.6825 .It's completely different from mine.Clearly I found the 'mean' but I doubt 'range' stand for 'mean'.

And I think the sentence of 3 is quite confusing.unsure whether use 1.5-2.5 is proper.
Reply 319


What value are you using? Works perfectly fine with n=35 to me. n=34 gives an answer below 0.9. I used the sum function on my calculator to check in the exam.

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